I own a pair of the new Martin Logan Ascents which are equally as good as the old reguests.(as stated by martin logan I have never dont the comparison who cares) And I use a Mark Levinson 335 which handles the bass better than anything I have yet to try. Tubes on logans?(NO WAY) The older series logans have a problem with the bass intergration to begin with and I dont feel tubes would help that.You need a really clean and fast amplifier on those speakers. Some people swear by krell, they say its a match made in heaven I disagree. I found the newer Levinson gear to work wonders on the Logans but thats my findings you may have a diffrent view? The Levinson amp in your budget would be the 334 @ 150 watts into 8 ohms per side and 300 watts per side into 4 ohms and so on. They sell for 6,000 new and they are about 4,000 on the used market or maybe cheaper if your lucky. Good luck with that amount to spend you will have a nice amp in your system shortly.