Anyone used a REL T-Zero

I can't comment on the Rel sub specifically, but I've been using a Naim N-Sub for a while, and I wouldn't be without it now. My main speakers are Kudos X2s, so not tiny like your Iotas, but still small as floor standers go. What I like is that the sub is hidden behind the sofa, so I get more low end clout without having a big pair of speakers that would dominate the room too much. It took quite a bit of trial and error with room positioning, and adjusting the gain etc. to get the balance right, but well worth it in the end.   

I used to run a REL Strata II to augment my Focal 816 SWs. I felt it worked pretty well, though I'm sure that was largely down to expert setting up by my dealer.  When I moved to Focal Electra 1028be the sub was mostly redundant and I moved it to my home theatre system.  That said, if I had stand-mounts I'd give a sub another go.  I've heard a friend's system where a sub integrates very well indeed.

M     

I have heard one when I bought my Iotas. My dealer did a good job in demonstrating them but I just didnt need / want the sub for my use (Iotas on the end of sonos / 72/HICap/140 in a small spare room). 

For or a main system I can thouroughly recommend the addition of the sub.  Not only does it improve the bass it really fills in the sound. Much better with than without I'd say.

I ran a rel T2 with a set of PMC DB1s and it did a great job. After a bit of tweaking it really filled out the bottom end but with control and great timing.

Go for it.   I have two REL T-7s (and before that two T-5s) and they are fantastic subs.  Very musical and easy to integrate with the main speakers.

I recently added the slightly larger REL T-5 to my Harbeth P3ESR set-up, and the results are spectacular.  The sub was very easy to integrate, too.  The added foundation is a welcome but expected addition.  But contrary to the lyrics in a popular sound, it's not "All About That Bass."  The midrange also opened up in a beautiful way, adding depth and recording space ambiance when present in the recording. The mid-range improvement is, I think, an overlooked aspect of adding a good subwoofer to a revealing system.  Worthy of a separate thread, I think.  

I use a B&W ASW610XP.  As others have said it make a considerable improvement - it also allows the main speakers to be placed to optimise their midrange and HF even if this causes a loss of bass response.  The sub can then be independently positioned to give good bass response while minimising any boom (or other odd effects) that would occur if you have to get all the bass output from the main speakers.

For an idea on how an interdependently positioned sub can be used, download a copy of REW and use the 'Room Simulator' to investigate different positions of the main speakers and the sub - it's quite revealing!

I have a rel t zero and it is a good little bass box for a small room but it isn't as good as my old bk electronics xls200 and they were similarly priced. The only reason I got the rel was for a bedroom set up and if it is for your main room the bk beats it hands down. The bk is 275 watts and has a 10 inch sub woofer  and the rel only has 100 watts and a 6.5inch woofer.

   The bk was on par with my rel r218 and that was nearly £900. If you need a small sub then yes it's good but if you want it for a larger room then I would look for a bigger driver as it will hit lower and have more presence. I used the rel on a musical fidelity m3i amp and tannoy dc4t speakers and it was a good set up for my small bedroom. The best thing you can do is try to have a home demo and see if it works in you're room