how I could improve my current setup.
Well. What you have already is excellent. You have obviously been prepared to invest in something decent which you expect to last for a long time. So really you ought to make the same decision again.
Get something bang up to date from an established source, for ongoing support. Cover yourself for any eventuaity over the next 5 years at least.
For what it's worth I had, still have, a main system similar to yours. Classic 9Ts twin 7" floorstanders with reflex transmission line paired with a powerful and versatile receiverer.
When digital and PC type audio started getting so much better and I started trying to ntegrate what were two more or less distinct systems (PC/Classic hi-fi) together I started with an M-Audio Fast Track Pro. Very quickly followed by a MOTU Ultralite. I also have a Native Instruments Audio 2 for mobile use. The MOTU and the NI are fabulous bits of kit.
That said there is a new generation of devices coming out now which attempt to address not just the conversion aspects (which is almost universally excellent now across the board) but also the control and flexibilty aspects. Think of an audio interface not as a stand alone DAC device but as something like the control section on an old pre-amp or receiver. A DAC, ADC, monitor controller, galvanic isolater, headphone amp, effects package, and multi switch all in one.
This product is a bit over our budget but is pretty much the ideal interface.
This is a long term favourite.
Get something decent. It worked for you in the past. Set you p for any possible upgrade path for years and years. Looks cool. Don't break down, Has residual value.