Where to go next after my internship...

Hi,
I am currently doing my final (masters) year of engineering at Oxford uni. and I just finished an internship in IT for one of the top banks.

What can I say - pay was OK but I turned down the offer as soon as I received it. The reason is that in a week I learned the tools they were using (Microsoft programming languages, databases, IDE's etc. - I'd never used them before) in the next 4 or so weeks I finished my objectives and for the rest 5 weeks I doubled my work. What does this mean? It means there is no challenge. Sure, in such a team I would work 9-16:00 or 9-17:00 with an hour for lunch and often a visit to the gym but I'm not looking to spend my life in such a relaxed fashion.

So did I like it? No - there was no challenge. And then I look at my peers - most of them doing "Management of IT and Information Services" degrees which will most likely prepare you for such a job well but for anything else you're scr3w3d. Anyway, I think management cannot really be taught as your main and only degree at such an early age when you have absolutely no experience.

I am interested in the high pay that banks offer but unlike some of my friends (both at uni and from the internship) I'm not prepared to do something that I find boring purely because it pays well. I think such a strategy is deemed to fail. Furthermore, I do want (although not as important as job satisfaction) to make a difference and try to rejuvenate the collapsed economy and increase the period such things happen(I do think that it could have gone much, much, much worse even though it was and still is pretty bad and maybe the worst is yet to come).

One of the areas of banks that seems to interests me is Quants. However, for that you need a PhD which I'm thinking and prepared to do but then quants don't make as much as say traders and traders only have a masters or bachelors. Furthermore, quants make no difference in the world with their algo trading. Also I would like to do an MBA but then I do the math:

Masters: 22
PhD: 22+3 = 25
MBA: 25:1.5 = 26.5 -> 27.

I don't want to turn into one of this individuals still going to school at 30. It's great but I think the world needs people who learn and then work and not just learn.

It's also very hard for me to know which area I would enjoy - you have equity traders, fixed income traders, IBD etc. and sure, wikipedia has articles on fixed income, equity and banking but I can't really get the hang of it from there. Is there a book that will provide a structured introduction to the sector? I'm looking for something that will explain what the purpose and goals of the different sectors are instead of me using wikipedia, starting at fixed income and after 30 minutes having ended on the Greek Debt Crisis or some irrelevant page to what I started with. Wikipedia kind of smudges the focus sometimes with all the clickable links.

On the other hand my knowledge is only technical - loads of maths and engineering. I am a very quick learner (all my final reports from the 3 internships stress that) but I'm not convinced banks are looking for smart people who can learn whatever needs to be known after they join the bank. It seems to me banks want people who already have the 1-2 months worth of knowledge that is needed to answer interview questions.