Choice for sub plate amp - phase/crossover?

[cheesehead]

OK, I've lurked long enough, time for my first thread...

I'm looking to build a sub for my system. I've got some ML-TL's I've built with the Vifa TC18's (first project - proof that I could build a speaker and have my spouse & kids like them ) and hope to replace those this summer with full range drivers prob. Fostex FE207E or FE167E in a TL. The system is used for HT & music.

I'm leaning towards the NHT 1259 from Madisound for the sub driver. (Other possibilites include Peerless XLS, Tempest, or the North Creek Poseidon kit.) The room is about 5 m x 8 m. I don't need to blow windows out (I'm way past that age ).

So, here's the questions regarding the sub amp:

1) Looking at response curves for the speakers I've built & hope to build (18 - 24 dB LF rolloff, f3 around 40-60 Hz; no, I've just simmed, I haven't measured...), I'm thinking that the std. 12 dB/octave crossover in most sub plate amps might not be enough for good integration? Should I spend more $$ and look for 3rd or 4th order? (I'll be connecting to the line-out sub out from the 5.1 receiver - would this provide additional HF attenuation?)

2) Is having a phase-switchable (0 or 180 deg) amp good enough, or do I want a amp with continuous phase adjustment?

Thanks for the help.

[officeboy]

Originally posted by cheesehead
2) Is having a phase-switchable (0 or 180 deg) amp good enough, or do I want a amp with continuous phase adjustment?

http://sound.westhost.com/pcmm.htm
I think that should answer your 3rd question.

[mightyjimbo]

Apexjr has a nice selection of plate amps for short money. Owner is on these forums as well.