For my sub amp, i was going to go with a JL 300/2 ($269) and bridget it. It's an A/B amp and that set up should get me 300 watts into 4 ohm with 0.03% THD with S/N of 108.5 dB.

I've been told that i should go with a single channel D amp. Choices would be 250/1 ($245) (JL recomends this for their Stealthbox) or the 500/1 ($338). This would give me 250 or 500 watts into 4 ohms with <0.05% THD and a S/N ratins of >95dB.

The D's don't appear to perform as well as the A/B, but is there a raason to use the D with Subs? I've read that they use less power to generate the power, but are not as clean. The 300/2 uses a 40 amp fuse, while the 250/1 calls for 30 and the 500/1 calls for a 50 amp fuse. Not much difference there.

Are D's better for subs? Why? Granted, i dont' think i could hear the difference, but would like to get the better amp.

 

Right D's are more efficient amplifers, but they should be only used on subs where clarity isn't as important. The are not "better" for subs just cheaper. Where a 2000w D is going to a lot cheaper than a A/B. Like you said though you won't be able to tell a difference.

 

As mentioned, affordability some, and efficiency for a lot of it.

Class Ds are much more efficient than a class AB amp of the same power. Say you were looking to get a 1500 watt amp. With a class AB amp, your going to be putting a heck of a load on your elecrical system to get 1500 watts. With a much more efficient class D amp, your able to make more power without the strain on your electrical system.
Amps CONVERT power, not make power...so, you need good power coming IN to the amp, to get good power out of it. A 1500 watt AB amp on a POS electrical system will get you nowhere near 1500 watts of output on that amp. Stick a class D on there and youll be seeing more power because its more efficient at converting power.

ABs are a little cleaner in general, but on a substage application, you will never tell a difference.