How much do I need to spend to get a preamp that sounds better than no preamp?

@analogluvr 
Thanks man! I appreciate kind words!

I installed a Hattor XLR late Friday. It took about an hour to begin sounding good, and maybe just now has hit its sweet spot. It certainly  solved most of the problems driving the 105 direct.

It has a lot more VC control, in addition to a significantly reduced noise floor and a much bigger sound stage. I was surprised by how much bass was missing from the 105 direct to amps.

If your budget is in the ~ $1000 range, I highly recommend it, BUT, it is such a microscope that it will expose lessor kit in your system. After a day with a Cullen power cord and PS Audio XLRs, I switched to Surf Cables XLRs (great audio bargain) and WireWorld PC. These significantly warmed up the sound. Pretty sure my Emerald Physics class D 100.2 SE amps need replacing now. Guessing the chips are 2-3 generations old.

I always scratch my head at "passives" with big heatsinks. 

@tweak1 
I read your other post and looked at the manufacturer's site. It's pretty obvious that it's being buffered. Given the heatsinks, the constant input impedance, and the fact it takes an hour+ to warm up, it's certainly got active devices in the signal path. Passives don't have parts that warm up or need heatsinks. 

Been my experience that all components have a certain "burn in" period. 

It's been a long time, but I remember even swapping cables, there is still an amount of time that it keeps improving, even though it may have been burned in before.