as Cerveza said it comes down to are you willing to do your own tech support.
I tend to shop through
www.pricewatch.com and google shopping to find absolute loswest prices.
one of the best things i've found that saves a ton of money is using branded OS. 82$ for 64bit win7Pro is cheap.
right now though I am saving up for the cooler above.
And you might be able to upgrade her current system (repacing CPU/memory) on the way cheap and have a better system.
but if your going intel go w/ at least a quad core (this will give you 8 threads).
and bare min of 4gigs but 8 will be better,
If you keep AC in office freezing ( for you peeps in suits ) stock cooler should be sufficient. If not loook at upgrading heatsink/cooler.
my opinion on Motherboards is go something really decent from 6 months ago that will handle todays top of the line CPU then find a cpu that the bottom has dropped out of the price. This way in 2 years you can replace that cpu w/ something better. With at least 4 slots for ram fill 2 now fill 2 later thing.
also make sure their are enough expansion slots for stupid stuff you might want to add down the road.
And if your really worried about tech support, buy locally. and I don't mean *spits*bestbuy*spits*.
Again just my 2 cents.
edit
also did you read the reviews ie. the negative ones