There really isn't as much bang for the buck with the IP112 I don't think. You're still paying for the amp and DSP but only getting it in a smaller package where it can't shine as much. Physics is still physics, but folks who've tried the IP112 will tell you that it's absolutely astounding what it can do.
The IP310 is flat out incredible. I've never heard so much volume and bottom coming out of a box that size. It literally sounds bigger than your average 610, and doesn't change tonally as the volume goes up. I shopped prices for an IP112 for a bit, and found some fairly good deals, but still kind of high, especially if you have to also add the 112ER extension cab to get more volume. The IP310 was moderately more expensive, but it wallops. Granted it is a bit heavy, and not something you'd want to carry to small gigs that a single 112 could handle. Or maybe you would. I don't mind the weight at all personally, and I'll use it as often as I can, or until I get tired of it.
A similar solution using separates wouldn't be light either. A good 410 is going to run 60 lbs. A moderate Crown XTI is going to by 18 lbs, plus another 10 lbs for a lightweight SKB to rack it in. That's 88 lbs right there, but of course you can move it separately. The IP310 is smaller, and with the castors is easy to move around once you hoist it in/out of your vehicle. And it would crush any 410 driven by a poweramp...no joke.
