The GX6650 has been getting attention as a competitor to Tegra's Kepler, but it's not likely to be its contemporary. The 6630 should be a closer match in terms of end product availability, and it should still bring with it quite a few of the 6650's competitive attributes like the six count of clusters and the "power gearing" and "triple compression" technologies (albeit in earlier, um, incarnations).
It won't have some of the significant architectural Series 6XT upgrades like the extra FP16 capacity and, perhaps of even greater impact, what I presume would be the rebalanced throughput characteristics of the XT refresh like potentially more triangle set-up, texture filtering, z units, etc. Hopefully, some of that was upgraded on the 6630 from earlier cores like the 64xx anyway, though.