This only applies to someone who knows what they are talking about.

[Liquid_force]

Are you sure? I thought i read that by audiobahn setting their sensitivity at high dB levels is what causes their subs to clip the notes. Maybe I'm wrong though and it was the amp that was clipping.

Pre98 is right. Speakers can distort in various ways - tinsile slap, reaching mechanical limits, decaying surround etc, but they can't clip.

Ford, extra power is rarely a bad thing if you use some common sense in controlling it.
Running your 200w sub with a 300 or 400w amp isn't a problem in itself IMO.

Have yourself a DMM and a 0dB 50hz test tone copied to CD(realmofexcursion.com has tones for download).
Once everything is installed and ready to go disconnect the sub (would be wise to disconnect other speakers as well, or just fade the HU to the sub only if that's an option).
Put your CD in and set it to repeat the 50hz tone. Set the HU volume to about 3/4. Bass/treble/bass-boost/eq's all to zero or off.
Set the DMM to AC volts.
Using this equation detrmine the voltage setting for the power you want your sub to see: V=SQR(P*R)
I'd go 200-250, so...
SQR(200x4)=SQR(800)=28.3
For 250 => SQR(1000)= 31.6

Using the DMM leads probe the bridged speaker outputs of your amp and use the gain/level control to set your voltage.
Once your V's set turn off the HU hook your sub back up and give it a listen.

I'm not a big fan of Audiobahn but if the price is right it should work as well as any other 300-400w amp.