If you're going to buy a DS-1 make sure it's one of the older Japanese ones - they actually sound good, unlike the current Taiwanese(?) ones.
The Little Big Muff was the first fuzzbox I ever plugged into, so it's kind of my reference point for fuzz tone, but not having heard the re-issues I can't say whether they compare or not.
One thing to note when buying gear - apart from guitars, where in many cases hardware changes have been made for the better over the originals, and CAD technology means there's little or no difference between individual instruments - is that re-issues are never as good as pedals or amps from an original production run.
The DS-1, along with the Rat and Tube Screamer are a case in point. If you don't want to get sucked into bidding wars on eBay for genuine vintage pedals, look at ready-modded ones from Analog Man - they'll be pristine and in full working order with no issues for slightly less than you'd expect to pay for an original with worn components.
The best vintage buys around (for now), I reckon, are the Ibanez 10 series pedals (ie TS-10) which are basically the same as the 9 series inside, but with an updated casing; they're far less sought after and still available for less than you'd pay for a new modern-day equivalent pedal (except, I'd imagine, for the TS-10, because it has 'Tube Screamer' in the name).
I agree that ditching the bass amp and putting the proceeds towards a valve amp might be your best option, but DON'T trade it in in a music store - they'll only offer you a fraction of its market value. If it weighs less than 30kg you shouldn't have any trouble finding a courier company to ship it, so selling on eBay is a good option. If it weighs more, try putting it in a local free ads paper or website before considering a trade-in.
One last thing: always buy used gear. Buying new just means you'll have much less to show for your money, and today's immaculate showpiece is tomorrow's lived-in workhorse.