Which pre-amps are better? From submixer or interface?

[pedwin]

Another question from the land of the "dummies".
Between all the hassle I had with the airconditioning I was also looking for a way to get and integrate additional pre-amps, as I only have two channels from my Avalon 2022AD. Due to my limited budget and two sceduled engineering courses I cannot afford to buy new ones. I know I could use the ins from the RME Fireface 800 as they also have build in pre-amps but I'm not 100% sure about that option. I also was thinking how I could use the pre-amps of my old MACKIE mixer (1402VLZpro) instead.

Which option woud you advise to prefer?
Another question that's keeping me busy is that in case I should prefer the pre-amps of the fireface, would the 1402 than be a kind of overkill as a submixer or can it still be usefull even with 32 channels on the main mixer (Toft ATB)? I am asking because I don't want to make the mistake of putting too much gear in my studio. I was allways impressed by people who achieve great recordings with a minimal amount of (high-quality) equipment. I would like to walk the same way.

Thanks in advance for all your advise,
pedwin