Well, really any amp will work. Channels refer to the number of speakers the amp will run at once (2 channels = 2 speakers, 4 channels = 4 speakers). Bridging means that if you have a 2 channel amp, you can combine those two channels into one channel at (a little less than) twice the power. So, like if you want to run your two 6x9s and, say, a subwoofer, you could get a bridgeable 4 channel x 100W amp, run your 6x9s at 100W each, and bridge the other two channels for 200W to the subwoofer.
Do not bridge an amp that is not meant to be bridged!
As far as the amp rating goes, I think 200W is a wee bit optimistic. Perhaps peak power. The difference between peak power and RMS (root mean square) is: RMS = average power. What that means is, RMS is what you get if you play one tone at the same volume and it never changes. The amount of watts the amp uses to produce that tone is RMS. Peak power is the power the amp can generate during, say, a drum hit. It's a short burst, and the Peak power rating of an amp can be many times its RMS rating. This usually happens with your cheaper amps. Speakers also will advertise really high wattage ratings, but that's just peak power. My pioneers, for example, advertise 250W of power, but they're really only capable of handling 75W RMS. Big difference, eh?
So, uh, having said all that, you should find out what the max RMS rating of your speakers is and try to find an amp that matches it. Say your speakers do 80W RMS? Get an 80Wx2(channel) amp. Or, if you want to run more speakers later, or your front speakers as well, an 80Wx4 amp. Or, get one anyway and bridge the last two channels for a sub.
If you want a "good" amp, stay with known brand names like Sony, Kicker, JBL, JL Audio, Alpine, Pioneer, Kenwood, Cerwin-Vega, and uhh... others. Lightning Audio is an OK brand. Just shop around, get what you want, not what they wanna sell you.
FWIW, I have two pioneer 6x9s in the back with a 70Wx2 Pioneer amp powering them, and 2 JL audio 10W1s in the trunk with a bridged 175Wx2 Alpine amp pushing them. It's LOUD in that car.
Hope this helps
