Your idea of a pair of SB-4000 is a very good one. As an owner of six SB16Ultras (2 stacks of 3 each) I'd say if you can stretch your budget, the SB16Ultras would be an even better choice and they are on discount now too, since the release of SVS' new 17" flagship sub.
I've used my SVS "six-pack" with Sonus Faber Aidas, Wilson Audio Alexx and now Avantgarde Duo SD G3 and I can guarantee you will not run out of quality, musical bass regardless of your main speaker choices in the future, even with a single pair of SB16Ultras