My perference:
b650 proart (only $269) > strix b650e-e ($350) >strix x670e-e > x670e proart
x670e proart is really not built for vfio/server. 2 nics, intel thunderbolt/usb4 controller. Those look great on paper. However, nics without sriov support are useless for vfio. All those features take away precious pcie lines, and no benefit for vfio. Also, you can see everything coming out of the chipset are usually in the same iommu group, which make it imposible to passthrough. Nevertheless, the last pcie slot only support x2 mode.
Because of all the reasons above, I bought MSI x670e Carbon instead. At that time back in Oct 2022, b650 proart was not in stock yet.
Here is my iommu group of MSI x670e Carbon. Primary GPU on the 1st PCIE. Intel x540-t2 on the 2nd PCIE, with vfs enabled.
Group 0: [1022:14da] 00:01.0 Host bridge Device 14da
Group 1: [1022:14db] [R] 00:01.1 PCI bridge Device 14db
Group 2: [1022:14db] [R] 00:01.2 PCI bridge Device 14db
Group 3: [1022:14db] [R] 00:01.3 PCI bridge Device 14db
Group 4: [1022:14da] 00:02.0 Host bridge Device 14da
Group 5: [1022:14db] [R] 00:02.1 PCI bridge Device 14db
Group 6: [1022:14db] [R] 00:02.2 PCI bridge Device 14db
Group 7: [1022:14da] 00:03.0 Host bridge Device 14da
Group 8: [1022:14da] 00:04.0 Host bridge Device 14da
Group 9: [1022:14da] 00:08.0 Host bridge Device 14da
Group 10: [1022:14dd] [R] 00:08.1 PCI bridge Device 14dd
Group 11: [1022:14dd] [R] 00:08.3 PCI bridge Device 14dd
Group 12: [1022:790b] 00:14.0 SMBus FCH SMBus Controller
[1022:790e] 00:14.3 ISA bridge FCH LPC Bridge
Group 13: [1022:14e0] 00:18.0 Host bridge Device 14e0
[1022:14e1] 00:18.1 Host bridge Device 14e1
[1022:14e2] 00:18.2 Host bridge Device 14e2
[1022:14e3] 00:18.3 Host bridge Device 14e3
[1022:14e4] 00:18.4 Host bridge Device 14e4
[1022:14e5] 00:18.5 Host bridge Device 14e5
[1022:14e6] 00:18.6 Host bridge Device 14e6
[1022:14e7] 00:18.7 Host bridge Device 14e7
Group 14: [10de:2782] [R] 01:00.0 VGA compatible controller Device 2782
[10de:22bc] 01:00.1 Audio device Device 22bc
Group 15: [8086:f1aa] [R] 02:00.0 Non-Volatile memory controller Device f1aa
Group 16: [8086:1528] [R] 03:00.0 Ethernet controller Ethernet Controller 10-Gigabit X540-AT2
Group 17: [8086:1528] [R] 03:00.1 Ethernet controller Ethernet Controller 10-Gigabit X540-AT2
Group 18: [1022:43f4] [R] 04:00.0 PCI bridge Device 43f4
Group 19: [1022:43f5] [R] 05:00.0 PCI bridge Device 43f5
Group 20: [1022:43f5] [R] 05:04.0 PCI bridge Device 43f5
Group 21: [1022:43f5] [R] 05:05.0 PCI bridge Device 43f5
Group 22: [1022:43f5] [R] 05:06.0 PCI bridge Device 43f5
Group 23: [1022:43f5] [R] 05:07.0 PCI bridge Device 43f5
Group 24: [1022:43f5] [R] 05:08.0 PCI bridge Device 43f5
[1022:43f4] [R] 0b:00.0 PCI bridge Device 43f4
[1022:43f5] [R] 0c:00.0 PCI bridge Device 43f5
[1022:43f5] [R] 0c:05.0 PCI bridge Device 43f5
[1022:43f5] [R] 0c:06.0 PCI bridge Device 43f5
[1022:43f5] [R] 0c:07.0 PCI bridge Device 43f5
[1022:43f5] [R] 0c:08.0 PCI bridge Device 43f5
[1022:43f5] 0c:0c.0 PCI bridge Device 43f5
[1022:43f5] 0c:0d.0 PCI bridge Device 43f5
[10ec:8125] [R] 0e:00.0 Ethernet controller RTL8125 2.5GbE Controller
[1022:43f7] [R] 12:00.0 USB controller Device 43f7
USB: [1462:7d70] Bus 001 Device 002 Micro Star International MYSTIC LIGHT
USB: [1d6b:0002] Bus 001 Device 001 Linux Foundation 2.0 root hub
USB: [1d6b:0003] Bus 002 Device 001 Linux Foundation 3.0 root hub
[1022:43f6] [R] 13:00.0 SATA controller Device 43f6
Group 25: [1022:43f5] 05:0c.0 PCI bridge Device 43f5
[1022:43f7] [R] 14:00.0 USB controller Device 43f7
Group 26: [1022:43f5] 05:0d.0 PCI bridge Device 43f5
[1022:43f6] [R] 15:00.0 SATA controller Device 43f6
Group 27: [8086:f1aa] [R] 16:00.0 Non-Volatile memory controller Device f1aa
Group 28: [1002:164e] [R] 17:00.0 VGA compatible controller Device 164e
Group 29: [1002:1640] [R] 17:00.1 Audio device Device 1640
Group 30: [1022:1649] 17:00.2 Encryption controller VanGogh PSP/CCP
Group 31: [1022:15b6] [R] 17:00.3 USB controller Device 15b6
USB: [0764:0501] Bus 005 Device 003 Cyber Power System, Inc. CP1500 AVR UPS
USB: [1d6b:0002] Bus 005 Device 001 Linux Foundation 2.0 root hub
USB: [1d6b:0003] Bus 006 Device 001 Linux Foundation 3.0 root hub
Group 32: [1022:15b7] [R] 17:00.4 USB controller Device 15b7
USB: [0930:1400] Bus 007 Device 002 Toshiba Corp. Memory Stick 2GB
USB: [1d6b:0002] Bus 007 Device 001 Linux Foundation 2.0 root hub
USB: [1d6b:0003] Bus 008 Device 001 Linux Foundation 3.0 root hub
Group 33: [1022:15e3] 17:00.6 Audio device Family 17h (Models 10h-1fh) HD Audio Controller
Group 34: [1022:15b8] [R] 18:00.0 USB controller Device 15b8
USB: [1d6b:0003] Bus 010 Device 001 Linux Foundation 3.0 root hub
USB: [1d6b:0002] Bus 009 Device 001 Linux Foundation 2.0 root hub
Group 35: [8086:1515] [R] 03:10.1 Ethernet controller X540 Ethernet Controller Virtual Function
Group 36: [8086:1515] [R] 03:10.3 Ethernet controller X540 Ethernet Controller Virtual Function
Group 37: [8086:1515] [R] 03:10.5 Ethernet controller X540 Ethernet Controller Virtual Function
Group 38: [8086:1515] [R] 03:10.7 Ethernet controller X540 Ethernet Controller Virtual Function
Group 39: [8086:1515] [R] 03:11.1 Ethernet controller X540 Ethernet Controller Virtual Function
Group 40: [8086:1515] [R] 03:11.3 Ethernet controller X540 Ethernet Controller Virtual Function
Group 41: [8086:1515] [R] 03:11.5 Ethernet controller X540 Ethernet Controller Virtual Function
Group 42: [8086:1515] [R] 03:11.7 Ethernet controller X540 Ethernet Controller Virtual Function
PS:
For onboad audio, in my case, it is a USB onboard audio. I just passthrough the parent USB controller. By doing so, I also get 4 USB ports passed through along with the audio device. I can use them for keyboard and mouse.