Boot drive upgrade

I have a secondary pc that I would like to upgrade the boot drive nothing crazy fast but something faster than the wd5000aavs that is in it. I will leave the Western Digital 500GB for storage so capacity isn't a big concern. all the hardware on the pc get a 7 in windows experience I know this is an almost meaningless rating but would like a hard drive that matches the rest of the hardware. Recommendations?

Get an ssd. 

Yeah its not a big enough issue to spend $150 on it. 

There are ssd's less than $150, lol. how much are you willing to spend? 

A 64GB SSD, large enough for a boot device and a few programs is around £45GBP (arounf $70).

Despite the WD being a 'green' drive, their still quite speedy and you'll be hard pushed to get something noticably faster unless it is an SSD.

Meh, I personally wouldn't go with a green drive. Blue is probably around the same price or cheaper, and it's rated faster. Blacks are even faster than that, but probably not too noticeably. I don't know though. I've never owned a blue drive.