In my experience ARC preamps are not the be-all end-all of tube equipment in general - (the amps are better than their preamps though). Their preamps are very thin sounding, sterile and can be down right schreechy!
The Supratek shouldn't even be looked at side by side with ARC gear. Yes - it will work well with your ARC amps (or any amp) but... as for preamps, the Supratek has the correct harmonics, tonal balance, and spatial characteristics that a preamp should have (and ARC lacks).
If you like ARC preamps - no-one is going to be able to tell you what you should or should not do because you have already developed your own bias. But given the price of the Supratek, you could very easily give it a try and see fist hand how this single piece of equipment can open new doors and take your system to an entirely new level of performance.
I don't even want to talk about BAT preamps vs. Supratek.