If you get the tone port you can do away with the mixer as the posher of the two has XLR ins and phantom power. It also moddels the Avalon vt737sp pre that I spent 2K on !

One thing to think about when considering a monitoring system is bi-amplified speakers.

Mixing will also be a lot easier if you got flat response amp/speakers.

Most stereo amps / speakers color (pleasantly) the sound coming out of them . You don't want this as it make you mix more difficult to translate to different types of commercial systems.

Flat response near-field speakers are good. Better are the same but with a separate amp driving each speaker.

Behringer Truths are a good place to start. You can spend as much as you want on a monitoring system however I think powered speakers start at about 130 bucks new. ebay is your friend here as well.