+1^ Like said in your old thread http://www.tomshardware.com/forum/301340-33-upgrade better gpus offer no benefit except for gaming or video editing/rendering since what you have can do everything else. Crossfire is just a way to "connect" gpus for more combined power.
Don, if you need help, I would suggest making your own thread, your 2 posts are in threads about hybrid crossfire and dual graphics, completely different situations and completely different cards (the new hybrid crossfire is called dual graphics to not get them confused). The 4200 can only hcf with 2400 and 3400 series. While the new a series can only dual with a 6450-6670.