Best Amp/Preamp Combo for around $6K?

Hi everyone - I am hoping you can provide me with a bit of guidance. I am looking to upgrade my current system with a new to me (used is OK) amp/preamp combination for around $6K. I like the "sound" of my current system (which I've owned for 11-12 years), but am thinking about upgrading. I have been told the Threshold amps are fairly strong in low frequency, and I would not want the upgraded system to have less bass. If anything, I'm looking for a "richer" sound. I prefer solid state if possible and would like the amp/preamp to the same brand. My current system is:

- Threshold S/250 (Stasis design, 125 w/c)
- Threshold FET 9/e (phono stage is not used)
- Naim CD5 (recently purchased)
- Alon II with Black Orpheus bi-wiring (~87 db)

I have been reading/researching this purchase for the past 3-4 months and think the equipment below would be an upgrade - unfortunately, no local dealer for auditioning!

- Rowland - Models 8T/10/201; SynergyII
- Pass Labs - X150/X250; X1/X2.5
- Plinius - SA102; M16P

Am I on the right track?
Best choice from brands above?
Any other brands to consider?

Thanks for taking the time to read this and your input is welcomed!