2 ch tube pre match for Sunfire Cinema Grand

How about the Modwright SWL 9.0SE? I paired it with a Sunfire Cinema Grand driving Aerius i's (Squeezebox > Benchmark DAC as source), and it sounded sweet. I've since upgraded to a Belles 350A Ref driving ML Summits, but kept the Modwright. The Modwright doesn't have XLR outputs, but DOES have Home Theater bypass, and remote. Alternatively, you might consider the Belles tube Pre (I forget the exact model number).

Firstly, the default Benchmark XLR outputs have more attenuation than the RCA outputs (at least mine do), so this makes comparison a little difficult. Once volume adjusted, I really didn't appreciate any significant audible difference. XLR should be less noisy on longer cable runs.

What the Modwright Pre added was
1) Taming the "digital glare" on some recordings (since the Benchmark is somewhat cool/analytical sounding direct to amp). No more listening fatigue with extended sessions.
2) Improved imaging and soundstage (not sure WHY it does this, but again, likely from adding tubes to the signal path). This is a lot more apparent with the Summits than it was with the Aerius'.
3) Provides Home Theater bypass so I can feed my DVD player(via a Yamaha RX-V1000) to my front ML's, with the Yamaha driving the surrounds and Sub.

Some argue that the best pre-amp is *NO* pre-amp, but it ultimately depends on your setup, plus room acoustics. If you buy a USED Pre, you're not risking too much to find out.

You can get a used Modwright for ~$1300-1500.

Another option I've considered is trying a tube DAC (or Lavry DA-10), either supposedly a bit warmer/organic sounding than the Benchmark, and which might work better direct to amp.

FYI, since replacing my Sunfire with the Belles 350A Reference (which, BTW, took overall sound to a new level) I hadn't tried the Benchmark direct-to-amp. Your posting piqued my curiosity, so I just gave it a listen... darn good soundstage and imaging, better than I recall with the Benchmark direct to the Sunfire! There is still *some* digital glare/sibilance in older recordings, but not as much as with the Sunfire. I'm still keeping the Modwright, but could be quite happy with the Belles/Benchmark pairing alone.

The Summits take a LOT of work to get them TWEAKED for optimal performance... overall room placement, degree of toe-in, panel tilt, adjusting dual woofer settings, etc. But after it's all said and done... the result is AUDIO ECSTACY like I've never experienced before! If you ever have a chance to hear a pair, go for it (but make sure they are properly set up).

IMHO, the only speaker that surpasses the Summits would be one of the old Apogee Acoustics planars (I actually owned the Stage during my audiophile adolescence).