I am starting to upgrade my system to build something simple but a little higher mid-fi. Recently replaced a Fluance RT81 with a VPI Cliffwood. Definitely realized some noticeable gains on clarity and bottom end tightness. Have this running into a u-turn Pluto hooked up to Audioengine A2+ with Audioquest evergreen cables. I like the sound, but also like the idea of making it better. I would like to stay with powered monitors for convenience in placement a space constraints. However, I wonder if upgrading my pre would make any gains or have I exceeded what is possible with the Audioengine. Any thoughts?
I have not heard any of your above components but it seems likely you have done well with the bang for your buck end of the market. The VPI should be giving you a taste of what is possible at the next step. There are good gains to be had but they will cost you substantially more than what you currently have invested in your other components. I recommend deciding which component to upgrade next and then putting money aside till you get to the $1000 - $1500 mark for each next component. That way you take a big step forward and should notice a good improvement. I would start with speakers for sure and if so see if you can stretch the budget there as it makes the most difference. I cannot recommend any powered speakers as I haven't heard many, other than gear like genelec (studio monitors) which may or may not be up your alley (very flat response without the typical audiophile clear and somewhat enhanced top end).
The AEs could be replaced with proper actives. Genelec, Yamaha, KRK, Adam Event, Klipsch and many others are out there. Better performance and clarity await.