Will an entry level tube preamp help w/ B&K ST-140

Do you mean Vandersteen 2CE? If so, I have been using a Tube Audio Design-150 by Bizzy Bee audio to drive my 2CE sigs. I had an ST-140, upgraded to the reference 4420 then to the McCormack DNA-1. The B&K to McCormack transformation showed me that I was missing some of the music. The tube pre created the wide and deep soundstage...

Eagleman

My personal recommendation is to consider some other solid state amp than the B&K. B&K uses MOSFET transistors in the output stage, which tends to make them sound rather warm and soft. A better idea, IMO, would be a SS amp that uses bipolar output transistors. Most of the top SS amps use J-FET transistors in the input stage (very linear for low level signals), MOSFETS in the gain stage, and bi-polar transistors in the output stage. In the systems I've heard that use a tube preamp and a SS power amp, the SS amps with bipolar output transistors have tended to sound best -- better bass control, better dynamics, and more transparent.

My comments are not intended in any way of "slamming" the B&K product line -- they make some excellent gear. If you intend to keep your tube preamp (which may be a good idea), then I'd make the switch to another power amp.

Do it. I'm glad I discovered how much a tube pre can help a system sound better. As a matter of fact it's hard to think of using an SS pre again. You'll find that the tube pre will take your system to another level over the Rotel pre. You can get varying amounts of "tubeyness" from different brands, something you may want to consider as I tried a Cary AE 3 and it was just too syrupy where the ARC LS 16 added just enough tube sound to make it wonderful. I had the Vandersteen Model 2's and suspect that with a tube pre you're in for a nice sounding combination. Your amp could be upgraded at some time but I'd sell the Rotel and get a used Conrad Johnson or ARC pre. These can be found for 5-700 in good condition. You really have nothing to lose as if you buy used gear here you can recoup at least most of your money, maybe more. You won't be wanting to sell it though, you'll get your more detail and 3d sound and it will also be smoother and more natural sounding.