Multiple sites with broad range, or multiple sites with narrow range

I'm interested to hear opinion on this...

We have a website selling 'lighting' products. We are looking to expand to furniture, and related items.

I believe 1 website would be easiest to manage, and build a good position in natural search... however - is this actaully true? Would having 3 separate sites, each one focussing on their range of products, with 'cross-linking' between the 3 sites be effective too?

So:
- expand existing site to cover broader range of products
- create 3 separate sites and cross promote

Which approach would you go for and why?

 

'cross-linking' between the 3 sites is realy effective.

 

Just use 1 site and build links to it.

 

yaa that's good idea first you optimize 1site after that second.
also you can start 3 separate sites and cross promote so its not bad effect but some time we can optimize 3site so you can get result after long time. first focus on one site its 50% done after that start new optimization.

 

If you're going to do 3 sites, get at least he home page of other sites indexed by Google quickly as new sites can rank poorly to start with.