I would humbly disagree: My car spends 90% of it's life on the road, and the bracing has made more of a difference than I ever thought possible. It gives you so much more feel from the chassis that you can push it further than you ever thought possible, confident in the knowledge that it'll give you more than enough warning for when anything starts to let go. That confidence alone is worth more than a few tenths wherever you are, road or track. Bear in mind I'm on stock suspension as well and I hate to think just how good the car would be with some really decent suspension on there...
That said, and to answer the OPs question, I think that your suggestion of just doing the ARBs is a pretty good alternative as well. If you choose the right ones and don't go too stiff, then you'll actively increase the cornering ability of the car without suffering from wheels trying to jump off the road when one side hits a bump. Jables, if all you want to do is to go faster with more control then personally I'd spend the budget on tyres (I love the Michelin PS2s for their feel and wet handling charateristics, but these are proving hard to get hold of in the correct sizes recently so I would also look at the Vredestien Ultrac Sessantas), if you want more feel but with increased body stiffness then the Summit/ GT Spec bracing pack (same thing essentially) is the way to go, or if you just want a little sharper drive through the corners then the ARBs is a great solution.
In an ideal world though, you'd do the lot and I'd argue that the car would be a whole lot better to drive than just sticking an expensive set of suspension on there, but that's another story...