Planning around the RAM probably isn't worth it.
First, price 1GB worth of DDR2. I can replace your existing RAM for $19.00 .
I picked two sticks, so I could run dual channel. (I wouldn't actually
do this, but this is just to make a point. At least some RAM now,
isn't that expensive.)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820134594
This AMD processor runs at 3.1GHz and costs $99.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103680
http://products.amd.com/en-us/DesktopCPUDetail.aspx?id=560
I can use the CPU Support page on Asus, enter that processor's name,
and it will return a list of motherboards. I'll pick one of those
as an example solution.
http://support.asus.com/cpusupport/cpusupport.aspx?SLanguage=en-us
http://support.asus.com/cpusupport/...0W,rev.C2,SocketAM3,Dual-Core&SLanguage=en-us
ASUS M3A78-EM AM2+/AM2 AMD 780G HDMI Micro ATX AMD Motherboard - Retail $79
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131324
http://support.asus.com/cpusupport/cpusupport.aspx?SLanguage=en-us&model=M3A78-EM
"Phenom IIX2 550 (HDZ550WFK2DGI),3.1GHz,80W,rev.C2,SocketAM3,Dual-Core ALL 1602"
So for $99 + $79 + $19 = $197, I have a kick ass microATX board with build-in
graphics and a fast processor.
On the Intel side, I might be able to find a cheaper board than
this, but I selected this one for the built-in graphics (and
the hope you wouldn't need to upgrade the graphics, for a while
at least).
GIGABYTE GA-E7AUM-DS2H $129.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128363
Processor list
http://www.gigabyte.com.tw/Support/Motherboard/CPUSupport_Model.aspx?ProductID=2946#anchor_os
Using this article, an Intel E5400 does slightly better than the
Phenom IIX2 550 (on SuperPI). On many other tests, the 550 is
crushing the Intel parts, and I'd have to go up in price
considerably to keep up. I use SuperPI as a metric when
comparing my systems here.
http://www.techspot.com/review/171-amd-phenomx2-athlonx2/page9.html
So I'll select an E5400 for now, just to get a price.
E5400 Wolfdale 2.7GHz LGA 775 65W Dual-Core $90
http://www.newegg.com/Product/Product.aspx?Item=N82E16819116076
My Intel system is $130 + $90 + $19 = $239
compared to the AMD at $197.
I can go with a less fancy Intel motherboard. This one is $60
and has two DIMM slots for DDR2 memory. So this is closer to
a budget solution. If I do that, then I have $197 - $60 - $19 = $118
for an Intel processor.
GIGABYTE GA-G41M-ES2L LGA 775 Intel G41 Micro ATX Intel $60
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128388
The best I can do for $118 is an E7400 2.8GHz Core2 Duo.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115206
So you can do an upgrade for about $200, with some choices
as to what you can get. I selected DDR2 RAM type, when pricing
motherboards, for best economy.
HTH,
Paul