If you are planning on keeping the LS25 I recommend an Audio Research amplifier. You can mix and match to your heart's content, but there is a rightness to the sound of matching amplifiers and preamps. Check out the Audio Research D400 MKII. It is a great sounding amp and it matches your preamp.
This is one of those situations where a trial of the specific combination would be ideal, though I can see how that might be hard when dealing with used gear. Tube linestages do not always "play" nicely with solid state amps--the results are somewhat unpredictable. Staying within the same brand is one way to avoid compatibility issues, particularly if you alread like the house sound of that brand.
It is hard to even roughly guess at what might work, particularly without knowing what kind of sound you are after. To me, the LS25 is a quite lean sounding linestage, so unless you want to emphasize that quality, one should stay away from leaner sounding gear. Rowland gear tends toward the warmer side (I personally don't like their Class D switching amps so listen to one first before considering such). I am a fan of the open and natural sound of Ayre amps, though these are not tonally on the warm side.
Have you considered having a machine shop make you some kind of tube cage?
Conrad Johnson MF-2500-A 240 WPC,Very powerful amp,yet it can do delicate too!I had one and had to sell it a few years ago due to financial reasons.Still regreting that decision! They come up used fairly regular,or call Spirit,bought mine there.Great service.Leans to the warm side slightly.Soundstage filled my room,went beyond the walls,very 3-D .
I should add that my CJ MF2500A was used with a tube preamp,Supratek Chardonnay.
I agree that the cj 2500A or cj premier 350 for that matter are very good ss amps. I used a cj premier 16 tubed pre with both amps and both were excellent. The 350 was the better of the two as it should be given the cost differential. You might consider McCormack or Pass as well.
I think the ARC SS recommendation is valid. I also think that one of the older Krell FPB series amp would also work well as would the Pass units.
The ARC D400 mk II is a good recommendation. If you liked the sound of the BAT VK 55 you may also consider a BAT VK-220 or 250.
I have an LS26 and am using a McIntosh MC402 with very good results. To my ears of course.
What speakers will you be using?
Thank you all, and keep the reco's coming! So cool and useful to hear people's opinions. To answer about speakers, I am using Definitive Technology Mythos STS. (http://www.soundstage.com/revequip/definitivetechnology_mythos_sts.htm)
The speakers have a powered subwoofer section that may sway amplifier choice, but I prefer that it does not sway such choice, as I expect that once I choose a good amp, it will stay long term, and the speakers may change sooner.
I'd recommend you decide on your speakers before your amp.
I will 3rd the CJ 2500a amp. Make sure it is an "a" version.
Also suggest a Quad 909 for only $700 used. Last, a Belles Ref 150 or 350.
I'll second the Magtech simply because they'll drive anything and are reviewed to sound great. Thirty day free trial period. Lifetime transferable warrantee. Low idle power. Low heat.
The c-j ss amps mentioned are indeed very nice, but be advised that no c-j products have balanced inputs or outputs.
Need to update my Magtech information.
On another audio site another poster and myself somehow both read, transferable lifetime warrantee. I recall being very surprised reading it on the website. After rechecking it is a lifetime warrantee on the Magtech amplifier which maybe the longest warrantee offered for a power amplifier.
Get a used Krell FPB cx amp. They work very well with tube pres, have all the power you'll need and last forever. My 300cx is almost 10 years old and has never had even a hiccup, sounds grand with my Wyetech Opal tube pre. Always looking to upgrade but I cannot find anything here that requires upgrading, other than tube rolling and installing Teflon caps in pre.