Consolidate Niche Sites into one authoritative site?

Hi everyone - hoping for some SEO guidance/advice here as I read conflicting opinions on this subject.

I have several ecommerce sites. 1 of them is our "main" site that is also one of the oldest (several years old). We also have several niche sites with the main keywords in their domain names etc too - they have a handful of products on each and are also several years old. All the sites sit well in the organic results with no SEO effort at all - guess we are lucky

We have never done SEO on any of these sites by the way but that is going to change since I have just employed a PPC/SEO person to help me get all this going.

Anyway - the old niche sites were all done by me with a copy of Dreamweaver , a $100 ecommerce template and a Dummy's Guide book by my side many years ago. We have grown somewhat since then and are all efforts have gone onto the large site we have and that is get 90% of the revenue.

However, the other niche sites still get good traffic but convert really really badly - they do have an "abandoned" look about them being few years old now to be honest. The old niche sites never get updated to be honest.

So, time to move on - our main site has all the same products too and actually sits better in the organic SERPS than the niche sites. The main site has 2000+ pages in google and has the

Here are my options

1) - 301 all the niche sites to the main site and close them down - job done. Problem here is our main site domain name does not, in anyway, reflect the products from these niche sites. Even though we sell those products (and better than on niche sites already - like 3 times better conversion rates) on the main site I would love to move the main site to a new domain but am way too scared to take to hit on even 301'ing this main money-earning site. The other issue is that we have multiple PPC accounts and this allows us to market the same product on 2 sites with 2 ads to 2 different domains. So we have a wider net to catch the PPC traffic

2) - Move the niche sites over to the same shared platform as the main site so we can maintain their content from 1 place and still provide niche sites with niche content and also maybe work on SEO on all of them. Problem here is duplicate content on different domains/same IP of course and the effort required to run more than 1 SEO project with limited resources. Benefits is we still have niche sites, all looking good and updated from 1 central CMS with their own PPC and SEO

3) - Move all the niche sites onto 1 new domain (we've had for a while but done nothing with it) that reflects our current company product range, using 301 redirects to do this. We could then do SEO on this new domain as 1 project along with SEO on our main site. We will have the same products on both domains but we could probably work hard to make it unique.

Phew - really stuck here - the developers are sort of saying "make a decision will ya!" to me which is fair enough.

So, in summary:

CURRENTLY:
1 main site does well, several niche sites that don't

OPTIONS:
1 - 301 niche to main site and close down niche sites. Easier for SEO but will miss out on multiple PPC ads

2 - Update niche sites to share same CMS as main site so easier to update - gives face lift. More SEO work but means we maintain niche sites with good domain names. More work though

3 - 301 niche sites to 1 brand new domain that we can build on over time. Meaning we have 2 larger sites though the current main one will still carry all the products that the new one does.


I am leaning towards option 2 though it means more work because I come from a niche site background. I also like the idea of keeping the multiple PPC ads. However, I could always turn the niche sites into information sites only and then offer links through to the products where appropriate - could still keep the PPC ads then?

Arghh - just created a 4th option!

Any guidance would be appreciated.