Best Subwoofer for Quad 2805 under $5k


Looking for musical subwoofer for 2 channel listening (Not home theatre!) that has the speed and finesse to keep up with Quad 2805s. Heard the Wilson Benesch Torus is an amazing combination, but don't want to spend $13k.
Thinking about the REL Gibralter G2 (carbon fiber driver) or the JL Audio Fathom f112. Has anybody tried these subs with the Quads? Any other thoughts?
vitman2020
Depending on room size, I would recommend a REL T5. Very fast sub which works great with my SF GH's and I'm sure will work great with Quads.
I have had the Rel T5 with my Quad 2805's and the Rel T5 is surprisingly very good with the Quads. Very fast and satisfyingly deep on a lot of music. However, I upgraded to the Rel R328. The R328 is in a different league with a 10" active and 12" passive. Very Fast,very musical and articulate deep bass. I am very happy with the R328 with my Quads 2805. Well under the 5k. The Rel G1 or G2 would be worth an audition. You can't go wrong with the Rel Subs.
I have Quad 988s with Electrostatic Solutions' maximum current upgrades and the Mye Stands filled with lead shot which provide a great deal of firm bracing for the Quad's driving panels. With the upgrades and the stands, my 988s have better LF performance than when stock, but they still roll off fast below 40CPS and rapidly lose LF impact. I submit that this is the reason that Quads are thought to be "polite" and are not known to good with pop and rock. I recently got an REL S-5 and now have it partially broken in and fully dialed in. The S-5 is not distinguishable and calls NO attention to itself, irrespective of how much very LF information is fed to it. The 988 sound has not been compromised by the addition of the REL. The REL is dialed in at about 40 CPS (the control that does this does not allow precise measurements other than the start point at 7PM on the dial of 30CPS and the end point at 5PM on the dial of 125 CPS. I have set the frequency cap at 9PM which means that its output is severely curtailed above 40 CPS.) The S-5 is fed full range by the output of my amps, as are the Quads. Frequencies above 40 CPS are severely curtailed by a filter circuit in the REL that has no impact on the full range Quads. When the REL receives information that is 40CPS and below, the impact, the power and the high definition of the LF information seems to be coming from the Quads - down to 20 CPS. Now, my studded up 988s are quite good with pop and rock and are no longer "polite" in the negative sense. All sources of music now have a strong and tight LF platform, which with Quads is transformative. This what REL calls a sub bass speaker is highly recommended for use with modern Quads.
Vtman-

REL is the best sub period! Any model will do in your system, especially, the "T" series. Even the older models are simply outstanding. Keep me posted & Happy Listening!