First of all, Power Acoustik is junk, so forget them.
Dont listen about MTX being better than Orion. MTX has went downhill in the past few years, and they are relying on publicity of their "Jackhammer" line and tricking ppl who dont know a whole lot about car audio into buying them.
Orion subs are amazing. If you can afford the power for the HCCA sub, it is a absolute monster. Theres better out there, but it will cost thousands. I never heard of SSL before, and Ive been working with car audio for 10 years, and been to a lot of competitions. Do not go with a off-brand amp. If you want the Orion HCCA 10's, you need a amp pushing at least 2000 watts rms, preferably more, because these subs are very underrated. Some good amps are American Bass, Sundown, Kicker, Oz, Rockford, Orion, and many more. Cheaper ones that are descent are Hifonics, and (I hate to say it) but Lanzar Opti is surprisingly descent (Lanzar is a lower end company but their Opti line is descent)
Pushing this kind of power is going to require a high output alternator and a couple extra batteries in the trunk. The more, the better.
Any questions, feel free to ask!