If I am allowed to build a recommendation....
PLEASE.. DO NOT FOLLOW YOUR PLAN ...of buying a new PC per bits, shares, etc....
As time goes by... you will find that the Hard Drive that you adquired a couple of moths ago,... has decreased its price because of a sale... of a newer more powerfull has arrived... the same as for memories... and for motherbpards,,, INTEL launched into the market the P4 850GB, a couple of months later the 850MV to reduce the amount of heat produced and introduce the newer, smaller CPU with 512 cache instaead of 256 cache...
In other words... in my opinion... build a PC through a time span is like getting maried by parts ( I hope the example will make it clear) or cleaning your body through the week....
I would recommend to save the money through tne time.... and when enouigh.... buy the best (trademarks/performance) you can... buying recognized trademarks like INTEL motherboards, Soundblaster cards, ATI or NVIDIA video cards....provide you upgrades/downloads via WEB pages in order to save the value of your product ... as time goes by.... and important factor to keep alive as MICROSOFT keeps changing Windows....
BEst Regards
Attilio
P.S. Long life to this forum....