Any experience with SVS 3000 Micro

Have you played with speaker placement to mitigate room issues? I think the SVS SB1000 Pro is a better (and cheaper) sub than the 3000 Micro and isn’t all that much bigger. The REL doesn’t go all that much lower than your speakers but may still help within its limitations. Personally I’d go with the SB1000 Pro as I think the bottom octaves the REL doesn’t have can contribute significantly to imaging, soundstage, and sense of space, and it comes with their helpful app for easier integration and has a 45 day risk-free trial (including shipping both ways) that I’d definitely take advantage of. BTW, I have an SB2000 and it’s very good especially for the $$$. Just my $0.02 FWIW, and best of luck.

I’ve owned the 3000 Micro for a couple of years and find it ideal for my application. It integrates seamlessly with my Merlin TSM MMI, extends bass low enough that I don’t feel I’m missing anything, adds presence to the sound, and visually disappears by fitting into a cabinet. I vastly prefer it to the little Von Schweikert sub I used to have, and also the 12-inch Rythmik I tried in this space. The latter simply would not integrate well sonically (perhaps because I had no choice but to place it in a corner) and was too big to hide. I couldn’t hide the VS, either, but at least it was down-facing and finished in lovely cherry, so not an eyesore. Keep in mind that this is a secondary system in a very large and completely untreated living room, with the Merlins located in a big, open-sided wall unit, therefore inherently compromised. But it still sounds really good, thanks in part to the Micro.

If you're trying to squeeze every inch then, yeah the 3000Micro is a great little sub. However, if you have a little bit more room I agree with soix's recommendation of the SB1000pro. It'll best either of your choices.

I had a pair of the 3000's in a 11.5 x 14 room and after some tweaking I was very happy with what they added. Depending on your room size they won't dive deep below 30hz but that's where the SB1000 will work better.