2.1 / 2.2 Request for Amp Suggestions


Recently, I purchased a Rogue Audio Cronus Magnum II and a pair of Magnepan 1.7s.

There's a noticable gap in the bass that I'd like to rectify. I don't use the system for TV/movies, though I probably will at some point. I prefer accuracy over thunderous response and am looking at the Magnepan DWM panels. My concern is that the power in the amp is definitely not enough to drive the DWMs, not to mention that the amp is already wired for the 1.7s at 4 ohms, so mucking with the impedance will probably result in blowing fuses and tubes.  The room size is on the large side. The 1.7s and amp seem to be matched right now, both for power and resolution, especially after rolling in a Telefunken preamp tube and getting the 1.7 placement pushed out to nearly 5 feet. Again, I'm absent the bass I want and am unwilling to muddy the 1.7 sound by pushing them back toward the walls. 

With this in mind, I'm thinking about using the preamp output on the integrated amp and connecting it to a secondary unit. What kind of amp should I use? I don't need an integrated amp as unit #2 and am struggling with the price of a Rogue Audio M180, even used. What would you do in this situation and why? 
128x128dunham_john
I would go with one of the JL powered subwoofers.  According to JV of TAS, the JL subs can match the speed of the Magnepan panels.  That will fill the hole in the bass
If you use the preamp output of the Rogue to use another amp the amp section of the Rogue will have no load. Tube amps need a load connected. If you use a subwoofer with an integrated amp you will have to run the speakers full range without the xover option. SVS has a 45 day return policy so you can try a sub and see if that does the trick!
https://www.svsound.com/pages/subwoofers
Driver size has no correlation to being slopppy or tight, a Rythmik F18 (18”) is super tight, low distortion, etc. any subwoofers from HSU, PSA, SVS, Rythmik, and JTR are good. JL Audio makes good subs, but overpriced, a $2500 JL Audio sub performs (and measures) similarly to an $1800 Rythmik sub. All brands I mentioned are also started/owner by Americans and their customer service are great, and all or at least most have their PhD’s in mechanical or electrical engineering, they know what they are doing, Rythmik for instance has many pages on FAQ’s of their performance, entries on phase matching for perfect integration, etc.
@yogiboy 
Thanks. I'll still be using the line outs for the Magnepan 1.7s. The preamp out is meant to be used in conjunction with the line out and not in place of it for the reason you mentioned. 

I'll check out the SVS, just so I can get a feel for the sound quality. 

Has anyone ever used the A120s that Speakercity USA used to resell? They look very similarly spec'd to the Rythmiks that @mzkmxcv (sorry, tag isn't working) mentioned.