Well as for the MS, both modelsport and fusionhobbies have stopped selling it(they were the cheapest in the UK). It was a limited edition because Tamiya must have been making a loss on each one sold. Sure you will be able to find one on ebay or rcmart still has one but it will cost quite a bit more than your budget with shipping. That's a real shame because I really rated this model with all the hop ups... Doesn't mean you won't find one on another site though, I just haven't looked.
Suppose you will have to go for the DF-03/DB-01 but really search around for the cheapest, every penny counts in this credit crunch!! There are lots of good websites out there offering good prices.
Keep it stock to start with then spend more over the next few months, means you don't spend so much in one go.
Good luck with the searching.