http://www.tomshardware.com/reviews/gpu-hierarchy,4388.html: Tom's Hardware ranks the HD 6450 5 tiers above Intel HD 3000 graphics (not that either one is super great).
http://www.anandtech.com/show/4263/amds-radeon-hd-6450-uvd3-meets-htpc/4: Not sure if any of the games they tested are games you planned on playing, but the HD 6450 handily beat the Intel HD 3000 graphics in all of the tests. Again, in many of those tests I wouldn't call the 6450's performance anything close to "stellar" (in half of them it struggled to get over 30FPS), but the smallest margin it had over the Intel iGPU was 15%, in some cases it actually delivered double Intel's performance.
Bottom line, it'll be an OK "emergency replacement" until you can save up...