The ever-useful graphics card hierarchy chart
http://www.tomshardware.com/reviews/...ew,3107-7.html tells all. Though the HD 2500 is not listed, it is almost on par with (a tiny bit better than, actually) the HD 3000 chipset. This is almost 3 Tiers below the 8800 GT, which was previously stated as a card that "would not be fun" to play on. However, at 1280x720 or 1024x1024 and on Low, it is likely going to be playable. The strong CPU performance from the i5 3450 is going to help, as the CPU will not be bottlenecked.
For additional reference, Crysis Warhead on low settings at 1366x768 achieved almost 40 fps on the HD 2500, although in BF3 it only achieved 20 FPS at the same resolution. So if 20 fps on low at a low resolution is playable for you, then I'd say go for it, but as a reference, an el-cheapo 7750 would give VASTLY better performance. Food for thought. Benchmarks for HD 2500:
http://www.anandtech.com/show/5871/i...phics-tested/3