Rolled off highs with unison unico: any solutions

Anybody have a problem (and hopefully a solution for)with the highs on the Unison Unico? My Unico seems rolled off in the highs: cymbels and small bells especially are way low in the mix in my system.
Here's the rest of the system:
SF concerto home
audioquest gr8 speaker cable
Sony C333es sacd/cd player
Tara labs prism interconnnects
Yes, all the rest of my system is soft on top. I'm wondering if switching the tubes (have stock inside now) will help brighten things up a bit, or perhaps switching interconnects. I"d rather not drop the speakers or cd player. Thanks all for any suggestions
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 agree with Mattybumpkin,
Try swapping the tubes with better quality NOS or good used tubes.
Don't be afraid of used tubes. Preamp tubes usually last a long time. Quality used tubes are available at reasonable prices.
Used power tubes are a different story.
Just my $.02.
Hope this helps, Rick.
Try some RCA Cleartops 12au7's, or Amperex 7316's. I did not perfer either, but you may like them since they both had extended highs. I found that almost any other NOS tube sounded better than the stock tubes that come with Unison.

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 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!