Wow, this thread might go down in TB history as worst collective advice ever.
What someone SHOULD have told you right off the bat is that if you're trying to have a gigable rig smaller than a 2x12 but with lots of bottom end for $400 or less, you are going to fail. It simply doesn't exist. The Bag Ends are supposed to be great cabs but not known for having a lot of low end. And I don't know WHY anyone bizarrely suggested Mesa 2x15s or a Powerhouse. That is like the complete opposite of what you asked for.
You cant really go smaller and get more bass usually unless you spend a ton of money. And even then there's just only so much physics can do with a single 12 or a couple of 10s. Unsurprisingly you went with a single 12 (albeit a higher end one) and are disappointed. You could try adding another but it sounds like your budget won't allow that. Something like one of those ported Eden 2x10s might be workable, but pricing wise I don't think they're a great value, and after A/Bing 2 basically identical Eden and SWR cabs, the SWR just sounded a lot better.
So you could spend $300+ on an Eden (or SWR or similar brand) 2x10, and still be chasing low end, or you could spend literally a few bucks more and get a Goliath 4x10 (III or IV for decent power handling, etc...). Yes, it will be about 25 pounds or so heavier than your Avatar and slightly bigger, but if you mostly use it at home, does that really matter? They don't have TONS of low end, but they have a nice balanced overall sound that should work for basically anybody. And they're cheap and plentiful, especially in southern California since that's where they're from. At the very least, you owe it to yourself to try a slightly larger cab that is known to be pretty cable and good quality so you have a better benchmark to advance from and see if it gets you closer to the low end you want. Other than that probably just a better 2x12 (or 2 single 12s) than the avatar, but that might easily bust your budget. And you might STILL be left wanting in the low end. Keep in mind that a bigger cab gives you a LOT more leeway with EQ.
The other thing is that for your usage profile, your amp is way overkill. You have a 900 watt amp to play in your basement. So with a much lower rated cab, you're not even able to open up the amp enough to get that low end. You should really also downsize to a Shuttle 3 or 6, or maybe even try something from a different company (not that Genz isn't great, just might not be what you're looking for). But definitely not higher than the 300-500w or so range.
Anyway, what was it about the size of the avatar that you had a problem with? Was it just that it was bigger/heavier than its level of performance? It doesn't sound like you're "on the go" all the time enough to really care about moving your cab once in a while.