I had the Unico and the stock tubes were horrible. Supposedly the Bugle Boys are extended, and might help. Very pricey though, so I would make sure before you buy.
I recommend you try the Solid Silver IC's from RS Cables($99) in place of your current Tara Labs. They work very well between my Unico and Jolida JD100. They will extend your highs, but are not bright. They do need the recommended 100 hour burn-in though. I like Mullards in my Unico, but I find that the sound of tubes you might like is a very personal choice......you have to try some to find out what suits your listening preferences.
Thanks to all for suggestions: oddly enough the highs came back quite clearly after a few weeks; I assume it was break in, although I haven't experienced that much change with other equipment. But thanks to your suggestions I purchased a new interconnect (kimber silver streak), that also made a bit improvement in detail across the whole frequency range. Thanks all!