Hey Muzza, best to test this sort of stuff out on a scrap bit of timber.

From the Outback Sunset & Coolangatta Gold DT kits I have used there is a lot of colour in those intensifiers and they really bring on a much more vibrant depth to the colour. Afraid that brown over the black will make it go dull. Acknowledge it may create more work using the different colours but should be worth it in the long run.