Picture of my setup thus far:
http://www.hiphopgateway.com/PDR_0210.jpg
I built my computer... and I if I could have just gotten a good dell, gateway, or HP...I would have rather done that... it was a lot more difficult then i anticipated...
Biggest THING! Make sure you get a quiet case and research CPU fans etc. My fans arent that loud but the case i have seems to vibrate everything and its loud as hell!
Mine has blue neons on it and all that stuff you think is cool when you start building... my advice is dont do the whole neon thing... maybe like a light dimmed neon thing is cool... mine is the brightest thing and just not really worth it in my opinion. i think it just sucks up energy plus makes hooking up more difficult...
Now onto your questions...
I like Athlon processors... they seem to be rated pretty good everywhere... I ended up with a 3.02 ghz Celeron (not that good of a brand but hey 3.02 for like $70) .. I got a motherboard CPU combo kit for like $150 offa tiger direct and for that price i couldnt pass up a 3ghz processor, my budget was limited... my system also has 2gigs of 133 ddr ram ... 133 isnt the best frequency ram out... actually one of the lower models of ddr ram but anyway... with 2 gigabytes of ddr ram... my system preforms very nice... got two gigs for about $200 offa newegg.com
If I could I would use a motherboard that supports SATA hard drives and of course you'll need to purchase a hard drive that is SATA powered too... Mine is 250 gig Maxtor(good hard drive brand) 7200RPM 7mb cache (i think) that i bought from tigerdirect.com for like $100 (great price!)
newegg.com and tigerdirect.com are gonna be your best friends...
But look around and be sure... i wasted so much time and money throughout building this thing...
Your most key features are keeping your system cool, noise, and of course having good specs... My shit was running at like 85-95 degrees until i upgraded the cpu fan... and that wasnt good for my processor, actually that might have been the reason my athlon processor went (that i originally had)... theres just a lot to look into... and be very careful with everything.... ESPECIALLY installing the CPU that you dont break it... my CPU heatsink & fan have to be screwed on and you could screw it on too tight and crack the CPU... just careful careful with everything... PLUS! DONT SLIP WITH A SCREWDRIVER AND HIT THE MOTHERBOARD... i did that with one motherboard and ruined it... and it was just a slight little slip... that must have cut one fo the lines on the board...
Well thats all the advice i have...
Whats your budget?