I’ve just upgraded to an i7-870 from an i3. I need to upgrade again in the future because its still not enough power, but its almost there and I’m using a hell of a lot of plugins etc. I have about 20 group channels, 15 fx with a couple of plugs on each and plugs into the vsts, as well as maybe 20-30 vsts I think - I use Batteries for each drum. If I broke that down a bit I’d probably free up some more power and that might be all I need.
I don’t know your original setup, but I came from an AMD I think, similar to the dual core around 2006 and the increase to an i3 was pretty dramatic. This upgrade to i7 has given me quite a bit of extra power, but I can’t test it fully until I get a new heatsink (old one has been broken all along and causing issues).
I opened up a song I was working on and the load dropped straight away. It was overloading before the upgrade. Because the heatsink fan is broken its hard to tell right now. I’ll open the track again in the next few days and put it to the test properly but at a glance it seems like a massive improvement. As a side note, I have Splinter Cell on the same computer and was watching CPU load on my second monitor. With the i3 it was peaking - oddly it doesn’t use all 4 threads, but both CPU’s - and with the upgrade the i7 distributed that load across 3 of the 4 cores and didn’t touch the other 4 threads. Loads of power to spare.
Beware if you are going to upgrade the CPU in future, I’ve just posted about this… Some Developers lock their software to the CPU - Native and Plug In Alliance for a start. Therefore if you open a track with the new CPU, FM8, Massive etc will lose the settings that you created. I opened a file, played it, realised it was wrong and then closed it, and because the synth sounds had all changed Cubase noticed the changes and asked if I wanted to save the track. Instinctively I hit yes and lost my work. Luckily I had a backup file and didn’t lose too much but it was a headache and ruined the whole day. Windows also had to mess about a bit and reboot before I could use the new CPU and the BIOS also needed looking at - I’m not sure if I even changed anything but I had a poke around.
If you are in the UK (looks like it from your post), I picked up an 870 for £52 from Computer Exchange. They have a few more in stock around the UK. If you make the upgrade then change the CPU at the same time if you are going to do it anyway. Save the headaches and just install everything once.