That 10Ah pack is going to be BIG. IIRC, there is more than half an inch difference between the 10Ah packs and the 8Ah packs in width. If you already have battery trays, it's probably going to take a bit more than a "little" modification to make them fit. The 10Ah packs are also about .7" longer than the 8Ah packs. That's a lot of space to try to find on a buggy chassis.

You also have to remember that the battery has to fit under the body. If you are only going to be bashing, I'd go with the 4S 5000mAh packs and run the MM/8XL on a 14/46 gearing (but no higher than 16/46). You should get lots of trouble free running with that setup. It's what I settled on with my buggy.

I'd also stay away from the maxamps 6Ah packs. Unless the copper tab cells are a significant improvement over the older cells, they won't deliver nearly the current they are rated for. All of mine self destructed with the same setup that you are talking about running.