I don't think any of these will quite get you where you want to go based on your room size --- you are already admitting you are well beyond the average joe in your bass expectations by saying two RW-12d's aren't getting it done. Those are decent subs, and one of the better 'budget' subs I've measured.
15x30 foot is a big room. My room is close to 19x27x7. It's right at around 3500 cubic foot. Two VTF-15 subs in my room wouldn't be enough for my preferences, I've had a pair in my room on a couple of occassions, and have had some playtime with the parir. They are great subs, but better for smaller rooms. In my friend's Luke Kamp's 1500 cubic foot room they are incredible. If you are seeking more than your pair of RW-12D subs you might as well go big, or you'll probably just find yourself at another stepping stone to wanting the next tier a year or two down the road. You can see how a pair of HSU VTF-15H subs compared to other offerings as documented by multiple attendees in the 2012 subwoofer meet linked in my signature. The 1000$ tier subs weren't really that much better than the RW-12ds that opened our meet. In fact I recall at least one attendee verbally commenting that the RW-12D was prefered over some of the more expensive pairs of subs at the meet.
With your budget you are looking at some DIY ideas, or saving a bit longer to buy a couple of bigger ID subs. You may also consider used. Ocassionally PB13 Ultras go for sale for $1100 ish in the classified section and those are nice subs for that dollar point.
I'm partial to the Rythmik FV-15HP after hearing one at that Gorilla83 meet in 2011, but I've never compared the sound quality directly to the HSU VTF-15H in the same room.
I really recommend something like the JTR Captivator for a guy like you in a space like yours, but in passive form your looking at $1700, then you buy an amp (something like an EP4000), and your at $2k pretty quick. It will be a sub that will knock your socks off though. There won't be any wonder if you've 'got there' or not.
Here are some other people's opinions to get familiar with.