Compared with your hifi spend “ a bag of sweets” (about US$300) - no offence meant!
Other things to consider:
If you are sticking with Naim amplification maybe but if not you may wish to move on as it may make sense to re-evaluate speaker cable at that time as well.
Lots seem to prefer silver plated ofc speaker cable but my speakers use ofc so I wanted to mirror this plus I seem to prefer copper (that is probably just me as most high end cables are silver plated). Deep cryo apparently improves conductivity but I’ve no way of verifying this objectively.
If you send your NACA5 unless you have some spare speaker cable you’ll be without for sometime (I just ordered new NACA5 but being based in UK I had other complications - process took about 5 weeks).
I’ve only just installed cables so would be wrong of me to say whether deep cryo NACA5 is worth it - perhaps in a month I’ll have a more informed opinion.
Sorry I can’t be more helpful/definitive.
@JosquinDesPrez just to add on to this, when I had mine done I was worried about being w/out speaker cables(no music). Chris sent me a pair 5m I think while mine were being cryo’d and re-terminated. I can share details one Saturday morning, but in short well worth it IMHO.
Yeah new NACA5 regardless of deep cryo will take time to settle in. Your Proac’s will love you soon enough.
A loaner cable isn’t a problem. I still have my WitchHat 10m pair of cables.
I’ll need to see what the cost is. What did you pay for the service on your NACA5? How long are they? I’m not so sure I’ll have my NACA5 cryo’d. There’s still a chance I’ll upgrade my 252/300 in the next year or two, and that would likely mean getting different speaker cables (Siltech?).
Edit: never mimnd on price. I see @Tapp answered that already.
No worries. I had two things done at the same time. Deep Cryo and upgraded termination.
Would you say that you prefer the NACA5 to Phantom? I sold my NACA5 shortly after getting Phantom but would probably prefer something with the best of both.
I’m using AVO cryo’d Twisted-56, nicely balanced and easier to handle than Naca5 but I still prefer Naca5, a bit more presence to the sound. All of Chris’ cryo’d products are great.
After using the Phantom for a few years I put the NACA5 back and decided I like it better after all.
I think it comes slowly but surely.
It’s really the first time an other cable hold the line so long and perhaps will definitely replace the little grey.
The olive musicality appears more and more with more other things (realism, naturalness, details quite such as an active system) than with the little grey and shows all the potential of the CDS.
I’m thinking to a past Naim fan who means this player will actually be not modern enough…
Probably a big very big mistake 
Phantom was and is significantly better - on my system at least. NAC A5 was ‘relegated’ to the second system.