Xplods and Blaupunkts are kind of mainstream car audio equipment, not the best but they're ok.
Bridging is pretty much what Jr said. You usually bridge an amp when you want to use it to drive a sub. A monoblock is an amp that only has one channel and is normally used for driving subs.
When bridging an amp, you use two channels and you get about double the power. Say you have a 4-channel amp with 4-50W outputs, you can bridge two pairs of outputs together and basically have 2-100W outputs.
The amps' outputs are usually marked as to which ones can be bridged.
When looking at amps, keep in mind that they'll be labeled something like "1000W Max!", "1000 music power" or something ridiculous like that. The actual power output will be much less than that. You want to look for the RMS power output as that's the true amount of sustained power you can get.
Take a look here:
http://www.bcae1.com/
That site has lots of info that you might find interesting.
