Luxman L505-u/KEF-LS-50/25' Run Speaker Cable

Well I guess the title says most of it, but I'm looking for some speaker cables to replace my Audioquest Type 4s. I'm not hoping to "tame" anything or change the sound in any way other than to improve all of the things the sytem currently does well: timbral accuracy, detail/separation, mid-range and upper mid-range musicality, airy highs, along with upper bass thump and a satisfying--to me at least--bass. It's good, don't get me wrong. But does anyone suggest a cable capable of accentuating all of these things and able to work over long runs?

OK, if I HAD to identify two areas for improvement, I would say better low volume performance--I have to turn it up a bit to hear the sound qualities described above. And sometimes with certain recordings the LS-50s can get shouty, a bit like the "Lowther shout".

Anyway, any ideas or suggestions will be greatly appreciated. Just wondering at this point. Thanks!
Lower volume performance cannot be corrected by speaker wire. It's a matter of amp and speaker synergy. It's a dynamic characteristics with impedance response plot of speaker and even more to consider. In you current situation, I see that your speakers would benefit from higher power I'd say 150WPC+ to get slight improvement of lower volume listening, but best way is to look to replace them. Also I'd continue to experiment with placement and listening position which is a challenge for open baffle speakers. Adding a sub is also another wise decision for your goal.
i've never considered money spent for high-end wire wise except i guess kimber 4tc unterminated bulk when i heard the most improvement of details vs. any wire tested for any price, but after considerations above you may just as well be OK with your current wire.
For longer runs I suggest you need larger diameter cables: 8, 9, or 10 gauge wire lowers resisitance and provides more current to speakers. All my online research in the forums indicates this. Supra Classic 6.0 is 9 gauge; Kimber 8VS,8PR, and 8TC are 9 gauge, and Blue Jeans Belden 5T00UP is 10 gauge. There is also Analysis Plus Oval Nine, 9 gauge, and AP Solo Crystal Oval 8, 8 gauge. Some of these cables are not too expensive and can be purchased on a trial basis. I have tried the Blue Jeans but it did not give me the result I wanted in my system; I still recommend it to try. I'm trying Kimber 8VS now. It has definitely filled out the sound. A fuller sound could lead to more enjoyment at lower volumes, by the way. Bass should benefit too. I'll soon get the Supra Classic 6.0 cable. My runs are 15 ft. After you try some larger diameter/ lower gauge cables, let me know how things turn out.
FWIW, I use a 20' run of Supra Classic 6.0 cable between my McCormack amp to Magnepan 1.7 speakers. Definitely can say it gives the perception of conveying every bit of power and nuance from the amp to speaker, whether playing soft or loud. Such a nice cable belongs on your short list if you require a long run.
Go for Luxman JPS 150! Best match for Luxman gear for the price.
I have LS50 with L-505ux and it works great. The cable is thick enough for long distance (5.5m2) and it's tonality match like a glove to the amplifier with variety of speakers.