Used MF Trivista 21 or Benchmark Dac1?

I'm looking for a new Dac in the $1000 range, and am wondering if it makes sense to go with a slightly older Musical Fidelity Trivista 21 or a Benchmark Dac1 or a PS Audio Digital Link III or a Bel Canto Dac3 (if I decide to spend even more). What's the downside of the Musical Fidelity? My system is all Krell, so I am thinking the tubes in the MF might soften it a little, though I have read the PS Audio Digital Link III may also be a good choice. Any thoughts?
Is a stock unit of the MF Trivista 21 acceptable on its own? How long can the tubes last before they need to be replaced? How many tubes are there inside the Trivista 21 and are these special tubes? Lastly, will a stock unit of the Trivista 21 add a bit of refinement with more open silky highs and lush midrange to a Krell KPS-30i CDP? Thanks.
Trivista 21 is a dac, so you need a transport; other than that, yes it's far more than acceptable as stock. It has 4 nuvistor tubes which reportedly last 100,000 hours! IOW, no you'll never need to replace them. They are pretty cheap anyway. I'd guess that it would improve your Krell, as your seek. I wouldn't say it strikes me as "lush", though. Cheers,
I did a direct comparison between the stock TriVista 21 and the Benchmark DAC-1. Now, I'm not the kind of person who believes A is clearly better than B. I'm a synergy guy. So for my system I enjoyed the TriVista more than the DAC-1. I didn't need the detail that the Benchmark offered. I was in need or timbral and tonal balance/wholeness that the TriVista served up. With other components I would have definitely preffered the Benchmark. I heard that the TriVista tubes last 100,000 hours (that's not a misprint). The only thing that bugs me about the TriVista id all the lights. Geez, I wish I could turn-off all of them except the 24/96 or 24/192 lights.
With your system, if your looking to "soften" the sound, I doubt the Benchmark is the right choice.

The MF or Bel Canto would be better choices I think.

I went through some similar gyrations lately and landed on an mhdt Paradisea and have been very pleased. In your price range, you might consider the mhdt Havana as well.