Should I consider the newer Audio Research pre & power amps, when I play records not CD's

TonyKay, the SP-11 is not one of the legendary ARC classics, hence it's lack of sale. It replaced the SP-10, which IS one of the classics. The SP-11 suffers from the subtly "white/dry" sound of the early ARC tube/ss hybrids, the SP-10 has an old-fashioned tube sound---lush, soft, sweet. Neither is as transparent and uncolored as newer ARC pre's, which can be had for less $ than the SP-10 and -11.

 The Ref 75 shipped with KT120 tubes and the 75se uses KT 159 tubes. But you can use KT 150 tubes in the Ref 75. Like all the fairly recent ARC amps that have vertical tubes. 

 I am not that familiar with your speakers. But I have a feeling something like the Ref 150 will sound a little more open with more well defined base My Elipsa SE speakers are rated at 91 db  sensitivity and minimum 50 wpc. I preferred the Ref 150 to the 75. But the only real way to know for sure is to try them in your system. 

 I had 2 systems. I sold a Ref 2 mk2 to upgrade to a Ref 3. Then the deal for the Ref 3 fell through. I put the LS 25 mk2 from my other system in the main room while I looked for a new preamp. After not being impressed with a demo LS 27.  I took home a demo Ref 5se for the weekend. The next Tuesday morning I called my dealer and told him I did not want to return the Ref 5se. How much would he sell it to me for. The Ref 5se  was that good I did not want to let it out of my system. I had to also sell my beloved LS 25 mk2 to afford the Ref 5se. So now I only have the main system.

 If you have to compromise, I would compromise a bit on the amp. You can always upgrade later. The preamp will have more of an impact on your system. Used the Ref 5se is a real bargain. It is just an incredible oreamp. It is easily twice as good as the LS 27. 

 I also own a DAC8. I am thinking of moving from a computer to an Aurender streamer. Maybe one with a build in DAC. The DAC8 or DAC9 for that matter does not work that well with  Aurender (or Moon) streamers. The nice thing about the Aurender is that it has a 2 TB hard drive so you don't need a computer. You can just copy your music files to the hard drive.

The DAC8 requires software which does not seem to be one of ARC's strong suites. I also own a Ref CD7. The Ref CD7 is very noticeably better than the same CD ripped and played with a computer through my DAC8. The DAC8 sounds best through AES and worst with USB.

 You may want to browse  AudioAficionado.org They have an Audio Research section, B&W section and many other manufacturer specific sections. 

I looked up your speakers and they are extremely nice. I love the workmanship and the sound must be terrific. Leave it to the Italians. I have a Ducati motorcycle. I purchased the B&W speakers because I have always loved them and the price was very good. They disappear better than any speaker I have ever owned. They are 90DB SPL and 75w would be the bottom I would accept in power. The 110w or 115w would be a little better. I am not a loud loud listener. I will upgrade them to a better pair as time goes on. No matter how good the equipment is "the speakers are the most important."
How do you get from the computer to the DAC without using USB? Do you use a USB to AES/XLR?  If I understood you the computer audio is not as good as a CD even with the DAC8 or other DAC units?
LS25mk11 For sale on audio Mart hope the link works.
thttp://www.usaudiomart.com/details/649316600-fs-audio-research-ls25-mk-ii-pre-amplifier/images/13894...
 

 That is a fair price for a LS25 mk2. I sold mine for $2400  a little over 2 years ago. Ask if the remote works. Audio Research no longer has replacement remotes for the LS25 mk2. It is a wonderful sounding unit. And one of the last of the truly nice classic looking ARC preamps without a display screen. The Ref 5se is suppose to sound best with the display screen turned off. So I never got the whole point of the display screen.

 I use a cheap GUSTARD USB Converter to go from my computer to the DAC8. First keep in mind that the Ref CD7 has a better all tube DAC inside. The DAC8 is solid state. Also there are a lot of variables with computer audio. They are not built to play music. Computers are noisy (RF/EMI) and it takes work to get them to sound good.  The Aurender is a one piece unit with a hard drive that is built to play music. You don't need a computer. If I got one with a DAC, I could get rid of the DAC8, USB converter and extra cables.

 They are truly beautiful. I got a real super deal on my speakers. They were a dealer demo and less then a year old. I don't think they were completely broken in when I got them. I listened to them a few times and really loved them. They are not the type of speakers you bring home for the weekend on a whim. Then I read a review that said. Some speakers sound this way, other speakers sound that way. The Elipsa SE don't sound any way. They just sound like music. I totally agree, I can't see ever wanting to upgrade them.

Go with all Herron Audio.  I haven't heard anything better.  IMO, VTPH-2 phono stage is as good as it gets, I haven't heard any line stage better than the Herron VTSP-3A (r03).  Amps are extremely good.  No coloration, no distortion.  Just the music.