Tube for MHDT Labs Paradisea+ DAC

I recently purchased this DAC from a fellow AG’er. Seller was not sure of the hours on the tube, a single GE5670 tube in the buffer stage.  I wish to purchase a replacement tube however not sure what to purchase. Any suggestions?

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When I had my Paradisea DAC, I liked the WE396A tube the best.  I tried several different ones and that was my favorite.
I'm using an MHDT Stockholm which is cut from the same clothe.  I have the GE5670, WE396a and a Bendix.  The GE is a nice all around tube.  The Bendix brought lots more detail and upper frequency extension.  The WE is superb in all areas so that one is my favorite as well.  I've only tried these 3 tubes and have no interest in looking further once I heard the WE.  The WE is Reasonably  priced to boot.

Mofi,as a follow up, I checked out Brent Jessee’s site and will probably get a backup tube different from the one currently in place. I believe it is the original GE5670. Brent has quite a selection.

When I had the original Mhdt Paradisea DAC my two favorite tubes were the Bendix 2C51 and the GE 5 Star 5670. The Bendix is nicely detailed with great imaging and soundstage. The 5 Star is a close second and was a very good value at the time. The 5 Star did not impress me at first, but with some burn in became more coherent and much better sounding. Some people like the WE 396a, but I found it to be a bit fat in the lower mid-range and bass. The D getter WE 369a tubes seem to be considered a bit better than the later O getter tubes.

I had/have a Havana so can't comment on the buffer tube in the Paradisea but I definitely preferred the Bendix 2c51 over both the WE 396a D getter or the Tung Sol which is also very nicely balanced. I suppose it depends more on taste and system balance as much as  anything. I preferred the overall detail and clarity that the Bendix offers. It's probably a good idea to try them all! In any case the MHDT products while lacking the last word in detail are still so enjoyable to listen to and a reason I can't part with my Havana.
Still have my Paradisea+ as backup for my Lampy. I have tried most of the contenders in mine including the WE396 and the absolutely best tube is the Bendix 6385. Be warned the Bendix is rare, quite expensive and might not be worth the effort.
I want to thank everyone for the comments. After listening to the Paradisea for a couple days I agree that, while lacking the last word on detail, it truly is enjoyable to listen to. Since I am dealing with a single tube, I think it would be fun to try several. Based on what I have been provided here I will look for a WE 396 and the Bendix 2C51 for contrast to the 5670 I currently have. 

On another note, what do users of MHDT think of the USB implementation? Have any tried a USB/SPDIF converter with one? I use Mac with Pure Music and CDs ripped to AIFF.