The numbers on CPU models generally don't tell you a lot.
You can look up a benchmark score for most any CPU here: PassMark Software - CPU Benchmark Charts
Most of the CPUs in your budget range would be in the "high end" or "high to midrange" charts.
For instance, the Intel 2450M is rated at 3583.
The charts give you a general idea of overall "horsepower" of various CPUs.
Differences of a few hundred points aren't likely to mean anything, but you'd probably notice a difference of, say, a thousand points in some circumstances.
Overall, you would probably be more impressed with a CPU that had a rating of 3000 in a laptop with an SSD than you would be with a CPU with a rating of 4000 in a laptop that had a standard hard drive. But I don't know if you can fit an SSD into your budget.
People game with laptops all the time---you just have to adjust your expectations to a lower level than on a desktop PC. Laptops just have gaming limitations due to their modest graphics and heat buildup.