As pointed out by some of the posters already on this thread, it comes down to the individual airlines. But as a generalisation I would agree with Man Flex. 1000hrs on anything is usually enough and that includes turbo-props and jets, if you are looking to use them for 'experience' purposes. Having said that, getting from 200hrs TT to 1000hrs TT will entail you learning a great deal more about flying and is probably some of the most valuable time you will spend in an aeroplane, as long as you don't let the twin/IR knowledge lapse badly.
The main thing in my opinion is to keep flying after qualification, especially during these hard times for first-time job seekers, be that through instructing or paying for a rating etc etc. There can be nothing worse than sitting there waiting for the phone call with 200hrs, to be still sitting there waiting for that same phone call 12 months later and still with 200hrs. I would consider that as an opportunity to have 700+hrs lost.
When I qualified with the princely sum of 250hrs TT I gave myself a cut-off of three months to get an airline job or else I was going to do something to enhance my TT. If you don't you are relying on luck to get a job and that was not good enough for me. I chose the instructor course as the only way I could see to get more hours and through that course I got my first break to fly light twins.
1000hrs piston single is certainly better than 200hrs piston single with 35 twin, but you need to be doing everything to keep moving on, as 3000hrs single is not doing you any favours in the eyes of the recruiters unless you are perhaps now examining, but I think you would need to be instructing twins as well...............
Hope that helps
PP