Matty, hit me up with a budget and what you're currently hosted on. We've got another dedicated on a diff network than the one I showed you before now and have been happy with that as well. I won't mention any of it to anyone; pricing is great on each. I'd assume that you're on VPS right now? 200 concurrent isn't unfathomable for that depending how you've config'd and there are a lot of vbulletin and MySQL tweaks and caching options that can make it serve a lot better when under heavier load; I'm not sure what you've done so far in that regard but if you're not data and query caching efficiently look into that. Also, make a new skin that displays less graphics, less snazzy features, etc. We use one that we joking call "Poor Mode" and force it upon all users when we start to hit too high of a load from social media traffic. It cuts avs, sigs, a lot of the buttons, etc and put it into a mode that disables other intensive features like search, etc etc whatever is using up a lot of queries.
Serving ads to everyone you should be wanting to hear from anyonene, not just premium; but I know how things go and that's why I bought VIP several weeks back and it is your site after all