Maybe SVS 3000 micro? Get 1 now and get another later? If size and WAF is a large concern, the 3000 micro comes in the same white as the SB-1000 pro, but doesn't have the black driver on the front. According to SVS, it is the sub to get when you have space constraints.
One thing to consider about the SVS SB-1000 Pro is that the onboard DSP + App combo allows you to have 3 bands of PEQ, as well as delay, variable low-pass filter slopes (with wide frequency range adjustment), etc.
I was recently in an audio store and was with a friend comparing the SVS SB-2000 Pro (what they had) to a REL t/9x (or whatever the big one is in that line). Before I connected to the DSP of the SVS sub, my friend found the REL to sound better as it didn't extend as deep and therefore didn't excite room modes and muddy up the sound.
All this changed when I connected to the SVS, applied some basic EQ to tame a nasty room mode, and set up the crossover correctly.
After that, it became very obvious that the SVS blew everything else in that showroom out of the water.
Hence my recommendation: Whatever you get, make sure to have room eq capability that you can adjust. SVS has built-in user-adjustable DSP which will save you money compared to everything else. Additionally, since SVS has that DSP onboard, they provide you with a much flatter (read: better) starting frequency response compared to the competition.