I'm new, so help me out...

Usually you want to match up the high end of the RMS rating for the subs with an amplifier that is capable of putting out that amount of constant power.

Also subwoofer are available in different impedances and must be matched up correctly to the amplifier for it to sound the best.  Most single subs are 4 ohms and most 2-channel amps can be bridged to use all their power to push that single 4 ohm sub.  But if you have two of those subs you can't bridge the amp.  Sorry I'm not real good at explaining stuff but I'd suggest to just keep on checking out the forums and you'll be surprised at how much you'll learn. 

Two places online that have very good info to get you started are Crutchfield's Info Center, and Basic Car Audio Electronics.

Okay here goes:

If those subs are 300 watts RMS (continuous power) then you need either an amplifier that will deliver approx 300 watts RMS by two, this can be achieved in a number of ways.

1. You can us a two channel amplifer that has the output power you are looking for.  If the subs are 4 ohm then find an amp that is 300w by 2 channels at four ohm (all of these are based on continous not peak power).

2. You can go with a mono block (one channel amplifier) for the two subs.  If both subs are four ohms then you would need to find an amplifier that delievers 600watts at two ohm, make sure the amp is two ohm stable.

3. This last option is probably not the best but it would work.  You can buy a four channel amplifier and bridge two channels together to make one channel, then you could have a four channel amp capable of running two subs, check the specifications of the amplifier to see what power output it has at 4ohms mono bridged into two channels. 

Again all of these would work and the numbers are accurate if both subs are four ohms single voice coil with an RMS power of 300 watts, post with the model numbers of the subs and I'll see if I can't help you out a little more.