I don't know what fits in your budget but JBL SRX 4719's can hit hard with a good amp. A microtech 2400 should do fairly well..don't forget to add cables and a crossover
to the price though. That is the low end reinforcement we have in our youth church and it can hit your chest. If you're using them outside I don't know if they are quite what you need for that. We used them outside on a macrotech 5000 once. I was unimpressed by them outdoors, but inside they will shake walls.
I helped out with a concert in the Missouri Theater in St. Joe MO and they had 4 boxes (8 drivers) of them on 2 microtech 2400s and it was enough to shake the stone walls. Pretty good subs, if you can afford them (or find them..I was having trouble with that) and plan to use them indoors.
I heard the Mackie
1501s in a gym at a church once and they didn't impress me. There were 2 cabnits, total (for subs) and I was unimpressed by them. I don't know if the operator wasn't really pushing them and they have more, or if they aren't too powerful. Either way that is the opinion I got from them without using them, they may be great subs, I just wasn't impressed when I heard them.