Which of the following preamps?

Looking to purchase a tube preamp either used or new at around 700.

I looked around Audiogon and found a few:

Audio Experience Symphonies Plus - 690
Sonic Frontier SFL1 - 750
Conrad-Johnson PV11-L - 625
A variety of used Audio Research LS for about 700 or more
Audio Miror T61 - 699

There are really quite a few out there so hopefully I can get some feedback from you.

Of the list you gave - I am familiar with Conrad-Johnson. I call tell you that all their preamps have a tube-like quality to the sound - and are well made with great warranty to boot! Not knowing how experienced you are in this hobby - I will tell you that once you get over $1500 price range (new price) - the differences in overall sonics are minimal until you get into the $4K territory. That does not mean that you won't prefer one over the other, just that above that range you're more likely to be looking at one area of the sonics.

I use a Conrad-Johnson PF2 Solid State preamplifier with a homemade single ended triode amplifier. Yeah, the sound is sweet!! Hope this helps!

Studio 1
I own / owned CJ , ARC and SF . The only one that ever required service is the SF. They all sound great. The CJ is a little warmer, The ARC a little more detailed. Both great your choice depends on the associated components and the style of sound you prefer.
May I suggest you consider the AES DJH Super Preamp? Especially outfitted with Polk NOS tubes, this simple pre sounds outstanding. Currently, one is being offered on A-gon.
One thing to consider is that years down the road ARC and conrad johnson will probably still be in business and offering support. That's one of the reasons I listen to an LS-16 in my system. This is not necessarily a recommendation for your system. Weiserb's comments on the sonic signature of these preamps are dead on.
What do you think about Audio Research SP9MKII?

There is one on audiogon now for 750.
The AES products are a great value and if you're willing to go a little higher there is a Cary SLP-88 on Audiogon for $950.

Do you need a line stage only unit or also one with a phono stage. If you need the phono, the SP9 could be a good starting point. But something like the LS7 with a more warm and rich tonality might be preferable. The biggest problem with the older SP series is their mediocre line stage which for today's dominant CD market, this is a big factor in a purchase. The SP products were really designed with phono playback as the primary sourse.

Just stay away from the highly analytical sounding LS1, LS2 and LS3 that sell in your price range. With these, you might as well go solid state and not bother with the added maintenance with tubes.

Another product to investigate is the BAT VK3. BAT products are exceptional value and get a lot of rave reviews here.

Years ago I borrowed an SFL-2 for a holiday weekend and this had great resolution and extension at the frequency extremes but the openness, bloom, dimensionality was severely lacking. So I suspect the smaller version SFL-1 could be very similar.

It comes down to what you seek here. There is a constant trade-off and balancing game between 3-dimensionality and getting great decays and space around the instruments vs. a more dynamic and detailed presentation. At your price range, you need to determine what is more important here and focus on a product that accels in that area. The CJ house sound is more to the former with the ARC to the latter. I would put the BAT in the middle.

I must disagree with the comment from Studio1 that the differences are minimal until you get to $4k. If we are talking about used market prices, products like the ARC LS5 in the $1500-2500 range depending on which version, and the BAT 31SE which I just sold here, both compete with and destroy so much of the competition that costs far more.

From my experience in putting together audio systems, I find the line stage to be the make or break point of a musical system. All links are so important but I found and heard many great products in the other links to maintain a highly magical and dimensional system. Unfortunately this is not at all true for line stages as I have found only a handful of products in the last 2 decades that bring on the "you are there" emotional connection to the performance. Why this is, who knows, but it has been a consistent observation.

Rather than just shoot in the dark here, try to hear products of similar topologies from these companies even if they are more expensive. This will give you an idea as to what the company's sonic focus is. But keep in mind that companies do some serious 180's from time to time in the sound of their product line.

Hi there,
I'm using an Audio Mirror T61 - had a problem initially due to a wire that had come loose in shipping.Probably been using the box for football practice!
This is a fabulous little amp for the money and imo it competes with kit 3x the price. Lose the Sovtek valves - I replaced these with NOS RCAs and it's hard to fault.
I have a Supratek Syrah coming but will be very surprised if it beats the T61 by a huge margin (saying that I hope it does but can't see what it can do better, except maybe a bit tighter/deeper bass)
The auto muting when changing inputs is a real bonus and if it matters at all, it's looks are always a conversation piece.
Rgds Si
would suggest a bat 3vki, audible illusions l-1
Try a Tube Audio Design 150 for about $800... Check out the reviews here on A-gon... It has a phono section...