The NAD PP-2i is a good starter preamp. There's a new NAD preamp called the PP-2e - it's an eco friendly unit that switches itself off when no signal is detected. Pro-ject make some good budget phono preamps as well.
Does your turntable come fitted with a cartridge? I think Pro-ject offer some of their turntables already fitted with one - possibly an Ortofon MM. If this is the case, you only need to connect your turntable to the phono preamp input, and then connect the phono preamp output into your Krell. Whatever phono preamp you get, there may be some adjustment required for either a moving coil (MC) or moving magnet cartridge (MM). I would guess that your turntable will be fitted with a moving magnet (MM), so make sure you select the MM option on the phono preamp.
Regarding the speed box - a good idea, but not essential until you sort the phono preamp first.
