Re the FX - they are modelled after classic fx units, so don’t expect something like an Eventide space, that said they are capable of sounding very good if you know what you are doing when programming your own, the presets are just ok IMHO. Also you get 4 fx so you can easily do more experimental stuff when using them in series or parallel. The weakest are the choruses and delay, just basic nothing fancy type things, the reverbs and moog style phaser are very good IMHO. Edit - I think that preference on sound of fx is very subjective, I really love the dark and plate reverbs, filter, comb filter and delay on the Octatrack and the reverb and delay on the A4 but plenty of people don’t, so probably try to listen to some demos beforehand just to be sure. Currently I am working on other ptojects so I do not have any examples to post but maybe some of the other guys do.
Re the pre-amps - I don’t find them to be very coloured, rather neutral in fact but overall a more analog sound than digital to my ear, I have had a lot of mixers and the Qu-Pac ranks among my favourites.
Overall though the main draw is the overall package, it does lots of things very well and a couple of things extremely well, in a small size, it has become one of the best purchases I have ever made, sure you could find better fx, maybe better pre-amps, maybe better eq or what have you, but to my knowledge not in the same price range or in a tidy well thought all in one out solution, I will continue to use it until it stops working and then I’ll probably try to find another.
It has sufficient depth that I continue to find new ways to use it, I am by no means fully au fait with everything it can do, I have not messed with DCA groups or matrix mixing yet, for a creative studio mixer it is to mixing what the Octatrack is to sampling, only perhaps a bit friendlier and also deeper.
A classic for the future!