CPU spikes in X2 and X1

Hi all, I am hoping (in desperation) that one of you may have an answer to my issue with Sonar X2. I seems to be the same as the original problems that forced UAD and Cakewalk to create a "sonar compatibility mode"...  [style="background-color: rgb(239, 242, 244);"]I had purchased a brand new Carillon AC1 audio PC with quad core, 8 threads, Gigabyte mother board, 16GB RAM working on windows 7 64 bit in May 2012 brand new. I have just (Feb 22nd 2013) received a brand new Carillon PC of the same very high spec but with an ASUS MB to replace this one in it's entirety as I believed part of the problem I am about to share was down to the PC... it seems it wasn't - and the guys at Carillon have worked very hard to try and help. I have always run Sonar, starting with Sonar 4 back in 2007 and progressing through 8, 8.5, X1 and now X2. I always keep updated with the latest patches etc. I have a UAD-2 quad card fitted in the PC and did have a brand new Focusrite Saffire 56 interface when I did the upgrade last May - but again, As I was advised over the months that the Focusrite could be an issue with my problem, I swapped this out last week (Feb 2013) for a UAD Apollo Duo. So I am now running my very High Spec, brand new Carillon Audio PC, with a UAD-2 quad PCIE card and a UAD Apollo duo interface. Here's the issue... I have the same issues with ALL tracks I have recorded, old or new but for this example, I have created a brand new project with 15 tracks of pure audio. 7 vocals and 8 acoustic guitars. I load on an instance of UAD 1176LN on every channel and also add one on to the master bus as I have always done - I really like the way that compressor works and sounds - I also add a UAD Precision Limiter instance on to the Master bus. In addition, I created a bus for reverb and I send each of the channels to there where there is an instance of UAD Realverb pro. Then I press play... It starts off the track and then the audio regularly drops out and spits and splutters and on some occasions when doing so, my 8 thread CPU meters SPIKE in to the red on the performance monitor in X2. the playback is completely unusable. The Disk reads 5% usage and the RAM 8%, so these are not even being slightly troubled... Carillon support have dialled in and can find no issue with the build of PC (don't forget, I have swapped it out to a brand new one just in case...) They have used a couple of testers like DCP Latency checker etc  but there are no PC issues. it's hardly being tickled... If I disable the UAD plugins, it still does it but not quite as bad - however it is still not usable. I have tried disabling the UAD completely (when I had the FR Saffire 56) but it still did it, so it is not anything specifically to do with the UAD kit being faulty etc. I have the ASIO setting set at default 512 on the Apollo - when I change it to 1024, it is better but still happens. When I go to 2048 it is now pretty much OK but this makes it impossible for me to therefore record MIDI etc at such a high buffer. i should be easily capable of running at 128 or even lower. I have spoken with the team at Cakewalk support numerous times in Boston over the last 10 months and get continually conflicting answers. Some say they have never had the issue before, others seem to have heard of it on many occasions. It has been suggested that I move my Synch and Caching up from 256 to 512 / 1024 / 2048 etc. I did this and whilst it seemed to make a little bit of difference, it is still there...  I have an open support ticket with CW Tech support There doesn't seem to be any other suggestions. As I said at the start, I have replaced my PC completely and it still does it. My PC vendor (Carillon) say that they have no other users with issues, although they don't see many people using Sonar much nowadays, mainly Cubase.  However, it looks like this fault CAN be replicated on other machines - Carillon are working hard to verify this and will update soon no doubt. PS - I have tried downloading X1 again - AND IT IS THE SAME. Any ideas? I REALLY want to use X2 as I have learned DAW with sonar since day one.  
However, I am at my wits end (it's actually starting to affect my health..., honestly) and I'm very close to either moving to Cubase / Protools or even moving to MAC / Logic etc. However, I don't want to do this... I actually really like Sonar, when it works. 
[style="background-color: rgb(239, 242, 244);"]Finally, I see on this Cakewalk post from Billy Buck that the "Sonar Compatibility mode" that used to be around on UAD was there because of this exact issue... If so, there must be a problem again. 
I do hope someone can help - currently, my studio (www.irismusic.co.uk) is not accepting any new business as I can't offer a service until this is put right 
Yours, in absolute desperation...  Scott  

My PC vendor (Carillon) say that they have no other users with issues, although they don't see many people using Sonar much nowadays, mainly Cubase

Hmm..

They didn't mention this to me 2 weeks ago when I had to send my AC-1 back for repair.
I don't thin the problem is with your computer or with Sonar - you need to look closely at all of your interface & buffer settings.

What happens if you bypass ALL of your plugins ('E')? Can you now lower the latency sufficiently in order to record Midi?

If so, then I think you need to adapt your workflow so that you have a clear distinction between the tracking phase & the mixing phase - one with high buffers, one with low.

This is not uncommon - I have to do this on my projects.