The "800 watt" PA5422 is actually 85 watts RMS x4 @4 Ohms.
The 2000 watts DA7122, actually produces 500 watts RMS @ 4 ohms, and 1000 watts @ 2 Ohms.
Honestly peak output is not a reliable way to measure output. Peak valuesbare the optimal (read as Best output achievable) under the most perfect of conditions.
69 Beers, fan cooled is a good feature, but I wouldn't limit yourself by making it mandatory. Several brands are well known for being heat resistant. I've had an old 200 watt (RMS) MTX amplifier stuff under a seat for 5-6 years, and it never cut out or had any issues. That includes several 8-10 hour car trips. Just make sure you get something with adequate power output (Remember RMS is the figure to look for) so you don't have to turn the gains up very much to achieve the volume you are looking for.
More power = less gain = Less heat = happier amp = better SQ.
I'd rather have more power on tap and never used, than a little amplifier pushed to the limit in a small, cramped area.
is just fine in my opinion. I wouldn't put them in the top echelon of brands, but they aren't in the low one either. I have heard some bad things, but I've also heard plenty of crap about Sony too. I've run subwoofers by both companys and have not been disappointed. My Audiobahn 12" DUB 1200 does the job wonderfully, if you could everything in the cab that is loose (and in some cases bolted down) rattling. So just search the net for reviews, go with your gut instinct. Ask here if you got any more questions.
Kenwood would be a good choice, if their amplifiers weren't so freaking big (at least the KX line) . Bigger makes for better heat handling, but you are not likely gonna fit it under a seat.
A MTX Thunder 404 would be good, or this INFINITY REFERENCE 7540a
would run nice and cool under your seat (while putting out around 111 watts per channel) Normally these run about $225 shipped.
If you're really on a budget, or just want to fill a void for now, then try out this Profile AP1040
. 75W x4 isn't too shabby for a little over $100 bucks shipped.