I feel a little strange disclosing my school, since it would be pretty simple to identify me as my program only accepts two PhD candidates a year, and I believe the other accepting PhD has already secured funding. Suffice to say that it's a well-respected program in the field. From reports I've heard, I could be reasonably expected to increase my earning potential by $15-$30K/year with a PhD over a MSci. Of course, that's dependent on what the job market looks like in the future, whenever I manage to complete the degree.
I just received the PhD offer sheet tonight roughly two hours ago by email, so I fired off a reply pushing for more information on funding. I'll probably go down to pester people for further information tomorrow. The quick expected turnaround for a decision is what's shaken me the most, although as you say I should be able to push to have at least until April 15. Thanks for the advice. I agree that taking out loans for a PhD program would probably defeat much of the increased earning potential.