Is that a home theater sub? You don't see 6 ohms too often in car audio. You'll want an amp that does something around 400W RMS @ 4 ohms and it'll end up closer to 250 when it's presented with a 6 ohm load.
Any chance it's a DVC sub? That'll let you wire it down to 3 in parallel. Same thing if it's SVC and you can get ahold of a matching second.
My only concern is you'll be wasting the amps potential pushing such a high impedance. That's not really a problem though
To be fair, design a decent enclosure for it and it should work fine. If you can post specs that would help seeing as how it's a 6 ohm. We don't know if it's single or dual voice coils or what. A 250 watt sub running at 3 ohms? Get a cheap 1000 watt and you should get around 250 out of it at 3 ohms. I recommend the Hifonics Brutus line on a budget.