I can't really comment much on that particular pre-amp as I have no experience with it. I will say that it looks like a good layout and well thought out clean design.
But, I did buy my ST-70 clone kit from Bob Latino, and he seems to be associated with Tubes4hifi, he is listed as the dealer on the east coast.
So, I have pretty good confidence in this company and in Bob. Bob will offer quick customer support, responds to emails on the weekend, etc. These guys obviously run this business as a passion project, and that shows in their products and customer service.
Personally, I would NOT pay more than about $1K for a 2 channel pre-amp, and that is already pushing it! So, yes, I agree that a kit is a much better option.
Don't expect a pre-amp to do much for you. A tube pre-amp will add some warmth though.
If you are still hesitant, I suggest giving these guys a call to talk to them about your goals etc. I never spoke to them on the phone, just email, but I think if are already leaning towards a purchase and you call and talk to them, you will most likely be buying a kit.
Edit:
I forgot to mention, I also like that Bob didn't try to upsell me on upraded tubes, etc. He was clear that if I wanted to spend a little extra $, then I should put the $ on Cap Upgrades, but ONLY the caps IN THE SIGNAL PATH. A snake oil salesman would have tried to upsell me at every opportunity, and try to milk those cap upgrades for the entire amp.