Upgrade from 7PE to 8.5 (or9) or invest in Komplete7 - how to spend my limited budget?

It's too early to tell what will be in Sonar 9, and you have time to decide about Komplete 7, since that doesn't ship for a while anyway. I'd delay the decision for a little while, at least until the feature list of Sonar 9 is released, which can't be too far away based on prior patterns... since you asked. :)

However, in the end, it might be a sound palette vs. Sonar 9 tools decision. What's more important to you? The "killer sounds" in Komplete (which will vastly broaden your sound library), or the "killer tools" in Sonar 9 (plus a slight-to-moderate increase in your sound library, probably)?

Buy when stuff is on sale if you're between 2.

8.5 has been cheap for an upgrade and that's the time to buy
Sonar 9 or 8.7 or 17.3 depending on its name won't be cheap to start with
Likewise Komplete 7 will start at its max and will go cheaper

In the end, I suspect you'll buy both, so buy both when they are on sale

Based on prior experience, the NI Komplete releases are usable from the get-go, whereas the Sonar releases are highly problematic (for a significant proportion of users, he qualifies hastily in a vain attempt to ward off the flames).  I now defer my Sonar updating until typically the second maintenance point release, which is historically early in the new year. So smooth your cash-flow and go K7 now and S9 in January - the best of both worlds

well if you go for NI komplete sell your battery 3, which is allowed

run the trial version of 8.5 if there is one (prolly will be one).. the first thing you'll notice is the engine.. it's not visible, but you do notice the change.
as for reason, as you know they are doing an update for 5 free if you buy record (£100- has reason 4 in the box) and you get record 1.5 / reason 5. they have changed NNXT for 5.. so can't say what it's like.

as for kontakt.. like me, well forget it .. Komplete is the way to go.. the price is to draw you to buy the lot.

what sorta music do you make.  when sampling, you use a lot , is tracking more important  ?

it's LOTS of questions only YOU can answer  , much like I have komplete.. Guitar rig 4 , I use as an fx unit.. others use it FAR more for guitars.. and me I use kontakt more... than they would :)

NI Komplete is a big outlay, but worth it in the long run (I bought v5 with kore 2) .

horses for courses as they say.

trial sonar 8.5 at least anyway. I think you PERSONALLY will notice the difference , regardless of what anyone here says

One thing to keep in mind is that Kontact is a sample player not a true sampler - meaning that it doesnt record audio from sources connected to your audio interface. For that you need to check out NI's Mashine / Motu's BPM or Emu's Emulator X 3. All are true samplers but Emu's product doesnt have a MPC pad interface whereas the other 2 do if thats your preference. Mashine has actual MPC style hardware included. I personally gravitate towards Emulator X3 though. Hope this helps!

Peace & Blessings

If you are running 64 bit, 8.5 corrected a lot of bitbridge issues.

Of course you will want to wait until mid-September before making any decision.