ok so ill address the CD drive first. Sure you could do digi downloads of your OS and all your drivers are online so yes you could go drive-less but I would not recomend it.
first a run down of how I birth a new or adapt an old pc : Cd install OS, CD install Norton anti-virus, Install FireFox, Install newest Drivers online via net, then backup/image system, and done.
I asume this is some what how most people do it or a vairation of it. Ok so risks of no cd/dvd
A. no cd/dvd drive so id have no anti-virus off the bat (win OS *** does not count) and would mean id have to go on the net to download it and all my drivers with out a rubber. Sure there safe sites but why risk a rig at all.
B. I'm a gamer I got a *** ton o games and some are old and need a disk drive.
C. There like 16 $$$ or a little more. Got old CD's i do, buy that ***....
OK NEXT! There was no post of a budget so i guess you can spend a little more but if not that's cool let us know. Its always good to post a limit.
Anyway so one gamer/PC builder to another if you got the extra cash, future proof your self. Not ballz to the wallz just so you dont have to buy all new parts in a year or two.
CPU: i-3 is getting pretty old tho still valid if ur gaming older stuff. I-5 is perfect for PC gaming and there not that pricy. (i got a i5-3570K my self and that's top shelf of gaming cpu's in the i-5's) IDK if you know but I-7 is really only for higher overclocker scores and hyperthreading and as of 2012 not a major role in games at all.
GPU: the GTX 650 ti is a really good card for the price, but i recomend the GTX 670 if you buy it. There's no reason to go above this unless ur doing some hard core rendering. also the ATI one is meh then again i dont like ATI so...yea...
PSU: 600 is cool for non overclocked but you might want a little more in case you do and for a future cards and maby even SLI/crossfire in the future (future being like 2-3 years or so)
MOBO: all about what you want to do with the pc in terms of how many GPU's, RAM slots, PCI ports, HDMI/DVI to connect to a HD TV and all that. If you get a good mobo u most likely wont have to get a new one for at least 3+ years. You got to spend $$$ to save $$$ unless your on a budget.
Tower/Case: not a bad pick might need to a a fan or two but then again im a full tower kind of guy.
hope this helps