Efficient Dynamic Speaker with low-end punch?

I second the Reimer line. The bass on these go very deep and clean. My 18 tube watts matches well with the Teton's.

Silverline speakers , new and used at your price point. Average efficiency 93 - 95 db, usually equipped with some potent woofers and a very pleasant/natural "House sound". An Aleph 3 would probably be a real potentially nice combination but try and get some tubes into the pre if you could. I owned that amp years ago and liked it a lot but didn't have the Silverlines (Sonata 2's) I have now. What is your pre? and room size?

let's get real my rocker friend! ditch the little amp and replace it with more power and get some real rock and roll speakers. $4K is plenty of $ to find a great combo from dozens of product lines. imo that nice little amp is holding you back from fully exploring all your options. also, don't forget about sub/monitor pairings. you could go the horn route but with that budget why force it? in the future you may also develop broader tastes that horns etc. might not handle as delicately. no offense to you horn lovers intended, just my personal tastes.

In keeping with Veroman suggestion, replace your Pass Amp with one of the new .5 series.
Perhaps a used X350.5 or X250.5

Zu Druid.