I use a
Session Direct Recording Pre-Amp, not sure if they're still available but it really does the business. You might find something similar under the Session Jerry Donahue (spelling?) box. Shouldn't break the bank either.
I can also recommend the
Line 6 Guitar Port......if you want to be spoilt for a choice of sounds then this might well be the ticket.
http://www.dv247.com/invt/7151/
Plugging straight in DI
can sound quite depressing without a little help