I don't particularly like Dell. In fact I hate them. But I won't tire you with working myself into a frothy frenzy... at least not right now.
Dell's prices are indeed, if you look only at the specs and what they would cost, hard to beat.
Still, I would argue that in the long run, it is cheaper and much more comfortable to live with many computers, if you build them, and rebuild them, yourself.
Also, while a lot of builders tend to turn towards edge systems, it's quite possible to build a credible little PC, cheaply. Check out this little exercice. No special offers, nothing on sale.
Sempron 2200+ $48
Soltek SL-KT600 or Chaintek SKT600 MB $39
256MB PC2700 $33
Rosewill 128MB R9600 $70
Case $17
Fortron ATX300GU $19
Samsung 7200rpm 40GB $45
Samsung or LiteOn CDROM $15
Good 17" Monitor CTX, Viewsonic, Philips... $110
Windows XP home $93
Keyboard Lite-On or DCT $5
Scroll weel mouse $4
$498 total.
$286 without monitor, OS, keyboard.
(I'm not sure of the R9600, I think Rosewill's 128-bit R9600 should be more like $80(?), so it's possible this card is the crippled version. Also, according to recommendations, that Rosewill card also needs either some underclocking or a little fan. Prices are from newegg.)