Amp Upgrade - 3k to 4k used?

Hi Folks:
I’m thinking of upgrading my amps and would value some advice. I currently have Blue Circle BC2 Monos. I’ve been really happy with them, but the upgrade bug is starting to bite again. I could spend about $3k to $4k on the used market. I’m particularly keen on tube amps (especially low powered SET), but not sure if my speakers would be efficient enough. I know my CD player is a little old too, but don’t think an upgrade here will get me a big bang for the buck. I’ll also consider upgrading IC and SC as well a little later on, but want really really good stuff (FIM or Valhalla likely). Another option may be to get a Shunyata Hydra. The rest of my system is:

Audio Physic Virgo II (89Db efficiency, I think)
Sonic Frontiers Line III – (but expecting delivery of Supratek Chardonnay in a month or so).
Nordost SPM IC & OTA Sakura IC
OTA Sakura Speaker Cable
3 Shunyata Sidewinder Power Cords, 2 YBA Diamond Power Cords, 1 pair of Bybee IC Filters, FIM outlets.

All advice and recommendations welcome. Thanks,
John, you might consider the Rowland 112. i know it is solid state but i owned one for 6 months and was very impressed by the top to bottom musicality and lack of ss etch.

i am a tube guy (Tenor 75Wp monoblocks) so that is where my heart is but at $3k to $4k used it is hard to beat the overall performance of the Rowland 112.

it doesn't hurt that the Rowland is a built like a tank and is one of the more beautiful amps out there. the older 112s have the polished case (like the #10 and #12) but the newer 112s have a cheaper black try to find one of the earlier models (it was costing Rowland too much to use that polished case for an amp in that price range).
Thanks for all the advice guys - some very good amp options mentioned - good food for thought. Cheers,
If you're eventually looking to upgrade to JMLabs Mezzo Utopia's, you may just want to save the $3-4k you're looking to spend on amps and allocate it to the JMLabs.

I suspect the change in speakers will be much more dramatic then changing amps. Besides, the amps you buy now may not mate as perfectly with the JMLabs.

Nevertheless, I think it would be worthwhile checking out the Manley, Rogue and Audio Research gear if you're looking for something that may give you a different perspective from the Blue Circle.
Keep those BC's, and send them back to Gilbert to update to BC2-8's (2500) or the BC2-8000's (4000.00). I would send my 2.1's back, but I spent way too much on audio lately. Check out the web page, getting 80% of the AG8000 (14,000.00) for 4k is a deal.
If you really want the BAT's with the Chardonnay, Mick will make 1 of the sets of outs XLR for $50. I know that doesn't make it balanced, but you could skip the adaptors.