Hi, i've been running a website for a while now and have seen a steady rise in sales, providing me with a bit of pocket money

. I have not advertised the website at all yet, both online and offline, apart from via google base and shopping search engine.
I am looking into (in the future) expanding the brand 'MT' into other markets, including-premium branded fashion, dvd's/blu ray and hopefully homeware. Every market that i expand into will have it's own website with the MT branding.
I hope to also have a corporate website once they are all set up (a long way a way) bringing all the websites into one.
My main question for you is, do you think it would be best to fully establish and advertise my 1st website (the one in my sig) before setting up all the others or, setup all the other sites, find suppliers etc and advertise them all at the same time?
Thanks for your time,
Ryan