new amp, old subs

just got a new amp, a sony explode 800W. have 2 12" MTX blue thunder subs rated at 250W RMS. the amp says it's rated 125W X 2 @ 4 ohms (max 280 X 2 @ 4 ohms) or 340W (monaural) @ 4 ohms (max 800W @ 4 ohms). k, first question: was thinking of running just one sub, due to size restrictions in trunk, am i in danger of overpowering the sub? or should i just run both, just worried on underpowering them. and second: building a sealed box for the sub(s) and going to replace the stock speakers in the deck lid with 6 X 9's and was wondering if the sub in the trunk will interfere with the performance of the 6 X 9's, or should i have them in boxes as well? car is a 91 sunbird. thanx in advance.

If you run both subs in a sealed box 2.3 cubic feet big they will fit fine in the trunk of your sunbird. The amp won't underpower those subs by enough to damage them but it will overpower one sub. I have had a lot of experience with MTX subs and they are will work well paired up with that amp.

with running both i'm just worried about running the amp too hard and destroying it, especially with the low boost turned up. any thoughts?

Well there isn't really a big worry with underpowering them. Doubling the power will only raise the output by 3db I would put them both in the recommended sealed box and use the bass boost sparingly. Correctly set the gain and you should be fine...you'll only blow the subs if you overuse the boost and crank the gain