I've owned many of the components you mention and have done a similar exercise.... So to answer your question, it all depends on the type of sound you like. When you add a good preamp in place of your HTS, you will immediately notice LESS BASS. I don't care what tube preamp you buy, they will not have the bass of your Krell. This may come to you as a big surprise and this may a relief. When I first compared to a tube preamp, it took me a while to really understand that the bass put out by the Krell was not necessarily "realistic" in terms of small scale music pieces because I was so focused on the fact that 10 to 20 percent of the bass impact was simply gone that I was unable to see it rationally.
With a tube preamp, the highs will become more liquid - wet sounding. More alive and less electronic and piercing. Easier to listen to and will simply envelop you vs. going right through you.
I ended up buying a Supratek preamp before I even A/B tested it against anything else out there. Yes.. I had owned other top brand preamps but the talk was so overwhelming about the Supratek that I just jumped in an purchased one for 2100 (new). I have posted elsewhere on this site about the comparisons I made between Supratek and CJ (16LS and ART) and the results were astonishing. I know people with $10,000 ---> $15,000 preamps who have switched to Supratek and say it transformed their systems to a degree they could not have possibly imagined.
Even with the Supratek vs. the Krell, some bass will be missing but, you will have a pure and beautiful midrange, tender highs and realistic bass.