I like putting the kits together too. It's very relaxing and always a prize at the end of the journey.
The Foreplay preamp from Bottlehead is always a winner. I think there are some options to make it very quiet if it hasn't been upgraded in the kit yet. Very nice preamp.
Marchand Electronics makes a passive preamp which is simple, clean and great sounding. Talk to Phil and he can make it however you would want.
The Basie I have is a stock unit other than the DACT attenuator. There are a whole bunch of "options" you can buy/use/replace the stock components with. I found in stock trim the unit sounded compressed and less dynamic than having no preamp at all. The bass below 50hz is also rolled off pretty well. This can be confirmed with an FFT spectrum analyzer too.
If you really want to build a basie then I would definitely email Brian Cherry. He is a very friendly gentleman as well as helpful. Feel free to mention what I find as short comings, He may know just hoe to change things. It's a good kit and a fine piece. It's just not musical and becomes entry level quality after only a short time of listening.
Bill