Hey,
I have a Macbook Pro 2007:
Modellname: MacBook Pro
Modell-Identifizierung: MacBookPro2,2
Prozessortyp: Intel Core 2 Duo
Prozessorgeschwindigkeit: 2,16 GHz
Anzahl der Prozessoren: 1
Gesamtzahl der Kerne: 2
L2-Cache: 4 MB
Speicher: 2 GB
Busgeschwindigkeit: 667 MHz
Boot-ROM-Version: MBP22.00A5.B07
Which was usually fast enough to run Cubase 5 with lots of processing etc.
Recently I installed Cubase 6 (latest) as well as most of my (native) Plugins (Waves 8, Voxengo, PSP, Drumagog etc) and - most important for me - Superior Drummer 2.3 - that way I wanted to work on things like Drumprogramming outside the studio. Time consuming stuff where I do not need the studio monitoring system.
Well, it was very disapointing.
Everything went fine, installing, iLok, elicencer, activation etc etc - but I have HUGE performance problems.
The CPU Meter in Cubase is about 40% but the playback is almost unusable as well as the whole system is sluggish and maxed out (checked in the activity app - CPU and RAM is maxed out).
That was a project which not more than 30 audiotracks, almost no plugins, just one instance of Superior Drummer.
I am using the Apogee Duett interface, first at 512 Samples, then at 1024 - no difference, and you see - no buffer related issue…
Is there anything what I can do? Will a RAM Update help somewhat? Are there tweaks? Are there processes in the background which can be switched of? Is there something set up wrong?
I am not very used to Macs…
I know that recent MacBookPros would offer me WAY more processing-power, but at the moment it is out of discussion to throw 2000 bucks out for a new Laptop. And I love the silver-aluminium design of my oldschool model way more 
)
Thanks a lot for any hint,
Brandy