Just curious if there are any disadvantages of going with a 2.5m pair speaker cable other than reduced flexibility (if future setup requires longer lengths) and increased difficulty in selling in the future. Speaker cables will be used with a non-Naim amp so the 3.5m rule does not apply.
Also, I have read that shorter speaker cables usually have slight advantages in sound quality due to lower resistance. Is this true?
Even Naim amps don’t really need 3m for stability anymore. That hasn’t really been a thing since the Olive days or earlier despite the manuals never being updated.
Most manufacturers prefer the shortest speaker runs possible, So it shouldn’t be a problem at all. There are two schools of thought:
As to which sound better, there is no one truth. Naim amps do sound better with longer runs of low capacitance high inductance cables (though no longer a requirement). Other amps may (and often do) respond completely differently.
I would strongly advise against looking for a single truth to fit all. Your amplifier manufacturer probably has their own recommendations. If you are talking about the Luxman, IIRC they similarly like low capacitance high inductance cables (JPS-100 is very similar to A5 in some respects), but suggest about 2m as ideal.
Thanks. I’m contemplating purchasing a used pair of (costly) 2.5m speaker cables, hence the question.
Out of curiosity, what sort of amp and speakers is this to go between?
Primary amp : Gryphon Diablo 300
Backup amp : Luxman L-590AXII
2nd backup amp : Naim 282/250DR/HicapDR
Speakers : Marten Duke 2 (primary), Graham LS5/9 (backup)
I’m not convinced one pair of speaker cables will be the right match for all of those amp and speaker combinations.
I plan to keep my existing Chord Signature XL and the new superior speaker cable will be an addition. Actually the Signature XL works fine with all speakers and there may not be any need for a new one, but curiosity is a dangerous thing..
I use 1m lengths of Linn K20 on my Denon AV amp in the office, main thing is them being the same length. I found K20 a suitable and fairly priced (as well as being flexible) option for various systems I have including my Sonos amp and my Atom on my lounge TV connected to in wall speakers where running the cables in was far more friendly and involved a lot less swearing than trying to do it with the NAC A5 I had to hand 
A friend has recently bought a very fine Quad 405.2, has an Ear Yoshino tube pre and Marten Monk speakers. We were trying speaker cables, I brought my K20s and everything sounded right, focused, dynamic.
Bear in mind the old Quads were actually designed with lamp cord mains flex in mind for speaker cable. The amps mentioned by the OP almost certainly aren’t. Though given some of the design similarities of the Luxman and Naim and similar cable characteristics, I might be tempted to try a 3.5 run of SuperLumina or short runs of Luxman JPS-1500. Both being heavy but simple multi stranded high end cables.
Mg understanding with “normal” amps is that, as a generalisation, the shorter the cable the better as it has less effect, with ideal being power amp right beside the speaker.
Bryston, for example, say “speaker cables should be as short as practical”
The problem being if you want short interconnects and short speaker cables, you have to put the hifi in between the speakers. Which some people (myself included) find extremely objectionable. If you don’t do that, you’re going to end up with, at a minimum, 4m of interconnects to power amps or 4m of speaker cable. You have to choose one or the other.
Not so bad if pre and power amps can connect with balanced cable
I have actually experimented with my WH Phantom 3.5m’s on a few non-Naim amps. A pair of 845 SET monoblocks and a heavily modified Adcom GFA-5500 (it’s nearly a Pass Aleph 1 at this point). Both actually preferred the longer WH over the shorter cable sets I had been using. Brands omitted intentionally.
I would expect the same results with Naim cable stock.
If the cable is having an effect you like, using them as some kind of filter, then longer cables would be likely to increase the effect. On the other hand if you’re wanting minimal effect from cables, liking the speakers powered directly by the amp, then shorter likely to be best
Lots of excellent cables @ryder Cardas Clear, WireWorld , Audience FrontRow, Shunyata. Are you in the US ? if so borrow some from The Cable Company.. The Marten speakers use those ceramic drivers ? I think Cardas Clear or Clear Beyond would be a good match, also Audience FrontRow Reserve is outstanding.
Do they make a Back Row? Where the action happens?
They do have a Back Row. That’s where they Grill Up the Halibut. 