Pre Amp or Interface?

[tastethepoison]

Hi Guys,
Im in the market for some new gear and Im really confused by the abundance of choices out there.

The gear Im currently using is a Macbook Pro i7 SSD 4gb Ram running Cubase 4 Studio with a tascam FW1082 as my interface/soundcard.
I also have a Joe Meek twin Q and a few mics.

Im looking a for an eight channel pre amp and Im not sure which is better for me. A pre amp like the Focusrite OctoPre MKII Dynamic or an interface type thing like the Focusrite Liquid Saffire 56.

I realise that one has compression and th other doesnt but are there any adavtages/disadvantages in buying an interface over a pre amp?

Would I still be able to use my Tascam FW1082 as a control surface if im using say a saffire 56 or profire type thing as my interface?

 

[ahjteam]

IIRC you need to have adat with octopre, so you would have to buy both

 

[tastethepoison]

Would I still be able to use the tascam as a control surface if I went for the sapphire?
And sorry but i dont understand what i else I would have to buy to run the octopre.