Hi Koestner. You are right on the money. The level of distortion and volume limitation low bass causes in full range drivers is unacceptable. It is the single most significant thing you can do. Room control is important but it will do you no good if your system is volume limited and distorting. I have made this AB comparison for other people many times. I use full range ESLs. By themselves they are big polite loudspeakers, good at Jazz and classical. Crossing to subwoofers at 100 Hz is like putting a turbocharger in a 911. Hold on to your hat.
There are several obstacles, finding a decent subwoofer and a good active crossover. For subs I suggest the Martin Logan Balanced force series and the KEF KC 92 also a balanced force subwoofer. This is an extremely important design feature, it helps to limit distortion by keeping the enclosure from shaking.
The best crossovers are digital. However, now you need four DAC channels instead of two. The inexpensive MiniDSP is a fine crossover, but the DACs are not so hot. The MiniDSP SHD Studio gives you a fine crossover and room control and you use your own DACs. Benchmark Media Systems uses this set up with their own DACs. That is a $6000 bill. Preamps such as the DEQX Pre 4, the Trinnov Amethyst and the Anthem STR have everything built in. The STR is under $4000.
I have no doubt that if you do this right you will be THRILLED with the results. Don't punt, take a full swing or you will just waste money. If you want to discuss this more please message me.