I'm a Primaluna Dialogue line user. I have the integrated model.
I think it would likely be an upgrade to go separates all around. But tablejockey is very right in his words of caution/disclaimer.
One thing that I would personally consider if I was doing what you are looking to do is listen to preamps with 6SN7 tubes. Primaluna is married to the 12AU7. They are a good tube, but I do like the 6SN7 sonic signature more. Some folks think the 6SN7 is the most linear small signal triode around. I do think it sounds a bit more at ease than its smaller cousin the 12AU7. It may be more prone to microphonics though--I'm not sure.
Take a look at this preamp--
http://www.dsachsconsulting.com/custom%20line%20stage.htmlI haven't heard the EVO line yet. I would think PL would engineer these to sound better when using its separates--otherwise why spend more for another box? I'm generalizing and giving PL the benefit of the doubt as they have a decent record of providing quality at pricepoints.