it all depends on how much money you have. What was your old amp that wasn't cutting it? an 8x10 ampeg is HUGE, HEAVY as hell, and pretty ridiculously overboard if your playing the amphitheater on sundays. I would suggest something light and powerful. If you got some money ($500?) Epifani cabnets are super light and the best i've ever heard. You could probably kill with a 3x10...
We play outside quite often though. I played thru a GK 1x15 the other day and that was not good for ****