$3500 to spend on a tube preamp....ideas?

I assume phono stage not required?

Consider the Ming Da Mc-2a3 for about 1k and throw in 1k worth of mods. Any competent tech can do the mods and make it rival anything thats out there. There are a number of fellow audiophiles here and on AA who can vouch for this statement.

Alternatively if you foresee using a phono stage, throw in a few more bucks and get an MFA Lumi. Can drive any long cables and any power amp even those with notoriously low input impedance, definitely a keeper for life.

transformer based attenuators work well if you have a source that swings voltage (like some DACs) and an amp with high input Z.

I prefer the Lightspeed to my most recent tube linestages - CAT, Lamm, ARC, Dodd, and the excellent Joule LA150 Signature Edition - I would save the $3000. That being said, the Mapletree 2A SE $800 with the Blackgate Capacitor upgrade is very, very good compared to the other more expensive linestages I have own, what is best is that it not only uses the 6sn7 tube, my favourite in a line stage, but with the flip of a switch it can also use 12sn7s which run half the price of 6sn7 NOS and sound indentical as far as I can tell. Include separate tube regulated power supply!! I had to own the expensive stuff before I could believe in well engineered, less expensive gear - the Mapletree is very well designed and you can buy an awful lot of music with the difference in price. Still, to my ears, the $500 is the best I've heard with a single source. If you want to spend more, the Joule preamps are wonderful.

This is too easy. Shindo Aurieges.

My new favorite is a Joule preamp. You can look for a La-150 or if you need phono then a LAP-150 preamp. Make sure you buy one which can be upgraded to the SE version later or buy the SE version now. Not all 150s can be upgraded to SE version.

IMHO, a used CAT preamp will most likely open your eyes as to what a great tube preamp can do. A little hard to find, but if you can get an SL1 Sig with phono or one of the later models, VERY hard to beat, again IMHO.