Yeah, your processor and RAM are plenty good enough. Here's some good options, maybe a little higher than you were hoping for, but anything else just isn't worth spending the money on to replace the one you have...:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150433
http://www.newegg.com/Product/Product.aspx?Item=N82E16814143069
Do you have a DVI monitor, or just a 15-pin D-Sub? If you don't have the DVI, you'll want to go with the second one; if you do, I'd go with the first one. The more RAM on board isn't a huge deal, but the first one is DirectX 10 compatible, which will be nice if you ever wanted to put Windows 7 on there...
If you can't afford either of those, I'd just stick it out with what you have until you can replace it since, like I said before, it just wouldn't be worth spending the money on any other "upgrade" for anything less...