A Computer For A Composer

So I'm an aspiring composer, which might also mean often unemployed composer, but I've saved up some money and I was hoping people could help me figure out my next purchase.

Currently I have an early 2008 MacBook Pro:

• 2.5 Intel Core 2 Duo
• 4GB DDR2 RAM
• 5400rpm 250GB HD

I use Logic 9 and Native Instruments stuff for composing, and when I have a moderate sized project three very annoying things things often happen:

• Loading Kontakt instruments, which use large audio samples can take up to 30 minutes, not great for productivity
• Too many synths causes a CPU overload, halting playback
• Sometimes the disk cannot write quick enough, halting playback

I'm considering an iMac because the MacPro is really pushing my budget, and a Retina MacBook Pro, while looking nice won't hold up in 5 years and i'll be in the same situation as now.

Unfortunately I'm not sure which sized iMac to get, so I'm open to input. I figure I need:

• Fusion Drive for the fast write speeds, but wether that is a 5400rpm or 7200rpm Fusion Drive who knows. Pure SSD is probably out of budget.
• At least 16GB of RAM. I'm not sure if NI software or Logic 9 can benefit much from 32GB.
• A decent CPU to stop the overloading problem, but I don't know how much improvement I will get from i7 over i5, or by having a bigger cache.

Just to stop any derailing, I'm not going PC or Hackintosh.

To encourage derailing for anyone interested, here is my portfolio website: www.MetzoPaino.com

 

Anybody?