I don't think Outlaw is very serious about their published specs as some of them seemed confusing and contradictory. I had to email for for clarifications before and got different answers from two different email correspondence. If you end up going with their products, I would suggest you insist on getting a response directly from their engineering/design team.
For preamp, if I need one now I would go cheap and get one of Topping's such as the $150 L30, or the higher end Pre90
Topping L30 Headphone Amplifier Review | Audio Science Review (ASR) Forum
Topping Pre90 Review (preamplifier) | Audio Science Review (ASR) Forum
One thing good about going with integrated is that you don't (or at least shouldn't) have to worry about compatibility, but to me that should not be a deterrence to wanting to go full separate.
You will have tough time finding a preamp that spec'ed and measured as good, for even 10 to 20X the price.
Parasound's $4,000 JC2 didn't measure that well, let alone the Z series would be much worse.
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