Subwoofer while running bookshelves full-range

The angel over my right shoulder has been telling me my current cheap sub (Klipsch RW-8) is fine; the devil over my left shoulder tells me I'm bored and should try something that goes lower/tighter and then I would find happiness in my job and relationships, etc. Seriously, I guess the goals would be to get something sealed, smaller, playing lower (music only, though), and Class D so that the auto-on feature will be more reliable and 0.5W standby (e.g., SB-1000). Except for a sonic upgrade, these other features aren't necessarily worth $500 together, though, so I haven't decided to buy anything. Wanting to get some opinions/experiences related to a number of factors in my situation. Not a pressing decision here, but might be worth the conversation, since I've only owned one sub in my life. Questions first, then all the stuff about my current context after that.

Q1: Opinions about running bookshelf speakers full-range and then just crossing in the sub at or below the -3dB rating on the speakers? On my Dynaudio X-12s, this is roughly 60Hz. I'm liking the results very much, but it's been a long time since I've had a receiver with a crossover to high-pass the mains. My amp has more than enough power, so I'm not worried about that aspect. Sub runs at 4 or 5/10 currently and is only 125-watt rms to start with, so I'm not using much grunt. If this approach is better than the ones listed below, then it makes choice of sub (or sticking with what I have) easier. (note that, until a few days ago, I had the crossover set higher and the volume down to 3, but lowering the crossover and upping the folume is a very nice improvement)

Q2: If I do the highpass/lowpass route, do you have experience with using speaker-level outputs on a sub as a connection strategy? There are discontinued Pinnacle subcompact subs I can get with this feature. But I'd be running the amplified signal through a series capacitor.

Q3: Opinions about running a short rca cable from my DAC to the subwoofer, and then using its high-passed (80Hz) rca outputs to the amp? The amp would therefore only be working on 80Hz and up. Sub is right by the amp.
This would actually allow me to switch between full-range and cross-overed on the fly, which could be fun if there are plusses to both approaches.

Q4: Granting that my current sub is probably mediocre (or lower, by most of y'all's standards), but that I've found it to be adequate without issues such as chuffing, localization, or anything like that, is it worthwhile to spend $500 to replace it? I'm looking at, say, the SVS SB-1000. if I get enough positive response here, I'll give it a shot and rely on their return policy.

Room and system:
Current setup: Dynaudio X-12s + Klipsch RW-8 sub crossed over around 60Hz. Amp is a TEAC AX-501 (class D with no sub out). I connect the sub using the high-level inputs using 12awg cables plugged into the backs of the X-12s.

The sub is an 8" with front (corner) port. Continuous phase and crossover. -3dB @32Hz.

I've managed to get what I consider seemless flat response. No idea at all at moderate volume that there's a sub, except that the image comparatively shrivels when I snap it off. I listen at low to moderate volumes (probably 70-80Hz). Sub starts to chug much over that, but I can't do that without putting the dogs and my GF outside first anyway.

Listening position 10' from tweaters, on axis, sub next to left speaker.

Room is living hell, and the big bottleneck in me ever going forward with a better system: essentially 12x24' with 9' ceilings (250sqft), some open doorways, hard flooring with rugs, one wall all with windows (cellular
shades). Sofa smack dab between the speakers, and dog on sofa until I cranck up Zeppelin. I've done what I'm going to do with treatments, and the results are "acceptable."

Thanks in advance.