Will spend $ 2500 for used speakers for upgrade.

My frist choice is B&W N803, is there any other speakers that you might like to suggest in that (USED) price range.
I bought a pr of the Von Schweikert VR4 Gen III for that price, I would also look at Aerial Acoustics 7b, and Tyler Acoustics.
Best of Luck
There are two pair of Soliloquy 6.5s on sale here on Agon. These are the top of the Soliloquy line They retail for $6,500 and they are listed for $2,250 to $2,700 here on the Agon. I have the 6.5s and I like them alot. There are also Silverline Sonatas on sale for $2,200. There are a bunch of speakers out there in that price range. Good luck.
I don't think you'll find used N803's for $2,500. If you do, and they
check out -- snap them up! In that price range, used. I would
recommend auditioning Sonus Faber Grand Piano Homes, Revel F-30's, and Monitor Audio Gold Reference 60's.
Dunlavy 4 or 4a would be bettered
I agree with RSbeck, you won't find 803's for 2500. I also agree that the Revel F30 would be an excellent choice.
Aerial 10T , but it likes a strong amplifier
Thiel CS3.6.
Legacy Signature 3.
Try to find a Totem dealer near you and give a listen to a set of Forests, very impressive.
Proac Response 2.5's. Trust me, you'll love them! They have a magical midrange reponse combined with outstanding bass and treble. You really can't go wrong with Proac.
If you have extra $900 dollars buy the diapason adamantes new, I am familiar with B&W,they are good speakers,But
this Diapason are just so musical,I heard the VR2, and the
Onyx,they are good, but no match to the musicality of
the Diapason,I bought mine used from Hongkong $1900,
I got lucky, Andy is awsome to deal with.I dont know, If
you can find used Diapason Adamantes, very rare.I almost
bought this speaker for 5k, when they first came out.
The reason they did not sell,too many competition for 5k.
For $3400 they are bargain.I dont miss my 15k speaker on
this speakers, very friendly.
I'd check the Legacy Focus for around that price. Not the new 20/20's but the previous model. I purchased mine for $2400 on the used market.