Okay, so tenkeyless keyboards appeal to people for ergonomics. If you often use the numpad, don't get a tenkeyless keyboard. You can purchase external numpads, but I find them cumbersome. Tenkeyless allows you to put you hands closer together, making it easier to switch from typing to using your mouse. I like both 104-key and tenkeyless keyboards, but it is really personal perference.
The mouse is one of the most opinioated parts of the compter; it is the part that has to feel just right for you. I love my Logitech g600 because of the high dpi (up to 8200), but it is quite wide. I also love my SteelSeries Sensei; it is much slimmer than the g600 and is a bit cheaper. As a brand, though, Logitech and SteelSeries are better than any other in my opinion. STAY AWAY FROM RAZER
I have the R1 of the Fractal Design Define XL and I love it; the XL R2 improves on some of my only issues with it, including the motherboard tray (which I don't like.) I will be modding mine by removing that tray and one of the HDD cages at the bottom in the coming months; Fractal is a great choice, fantastic company!
For a heatsink, you have several options. I went for the high(est) end air cooler, the Phanteks PH-TC14PE in black. It keeps my i7 3770k @ 4.6gHz idle at 29 degrees C, and under load (with Intel Burn Tester) at 70 degrees C. However, an alternative that I may switching out for is the Swiftech H220, which is a closed loop cooler (CLC) that isn't quite closed. Unlike others, like the H100i, Kraken X60, etc., the Swiftech H220 has a much more powerful pump (6x as powerful as the one on the H100i) and allows for opening to the expansion of loop to include additional waterblocks for your GPU, motherboard, etc., additional pumps, additional radtiators, pumps, etc. However, if you don't plan on overclocking, an air cooler will be just fine. I recommend Phanteks for air coolers, as well as Noctua. For fans, Noctua makes the best ones, but they are repulsive brown. They work so well, though, that people either put up with the color or dye them.
Speakers... hmm, well if you want a standard set, Logitech makes several 5.1 setups for a great price. However, higher quality audio recordings would be more suited for headphones, unless you want to spend $600+ on a 7.1 surround setup and a $200 soundcard. I don't have speakers, I just use my V Moda Crossfire M80 headphones for everything.
Well, for headphones, as I said before, I love my V Moda Crossfire M80s. They are a great value for their audio; don't take the word "value" to mean anything about the quality. For about $180, you get a very sturdy, well built pair of headphones that look great, sound fantastic, and are completely worth it. However, if you want something cheaper, go for some lower-end Audio Technicas or even some SkullCandies (I don't like them anymore, ever since I got my M80s :D).
As for monitors, if you have the money, get a 2560x1440p monitor. I am going to be getting the Asus PB278Q later this year, but a budget alternative would be to get a Korean-made 2560x1440, such as a CatLeap, on ebay and hope for the best. The crew at TekSyndicate has lots of Shimians around the office - they are very affordable compared to the Asus and Dell alternatives. However, if you don't want or can't afford that quality of a monitor, the good old 1920x1080p 24" is a great standard. For everyday use and some gaming, a good 1920x1080p will be fine. Just get what you can afford, but ask the community for feedback before you do :)
I hope I helped! Cheers,
Brennan Riddell