If money is an issue you'll be better off in the long run building your own system.
That doesn't really mean spending much (if any) more - just more legwork from you.
I've got an E6300 overclocked to 3.1ghz in an Asus P5N-E motherboard.
(a decent board is *key)
I've had the board for a while, and it will be a reasonable system for a while to come.
It overclocks well, has a 1.33ghz bus and accepts quad core chips as well.
In a year or two when quad core chips are cheap I can drop one in and get a serious upgrade for not much money.
The board takes up to 8gb of DDRII so I've got that upgrade path as well (I only have 2gb right now)
The board was close to $200 when I got it, but it's saving me a bundle.
The below components are going to be way better than what you get with the Lenovo for about the same cost.
Shipping will eat more money, but if you dig around you probably get everything from 1 or 2 vendors and cut that down as well.
$122 P5N-E
http://www.partspc.com/ProductDetails.asp?CatID=679&ProdID=6346$104 E6300
http://www.starmicro.net/detail.aspx?ID=729<$80 2gb DDRII 800 (not gonna recommend specific memory)
$53.98 500gb ncq sataII Seagate HD
http://3btech.net/se50728mbbus.html$57.99 NVidia 8600 gts
http://3btech.net/reboxpanvge8.html<$80 case w/ decent PS (not gonna recommend anything specific here either)
on edit:
I grabbed all that from pricewatch.com in a just a few minutes... which is why I recommended the site.