Hi, i can do your upgrade in few days it is not a problem, we can put it on development server first and when you decide we will put it on live server. I did massive migration few days ago from 1.4 to 1.7.1 and than to 1.9.2 (it need to be strict to magento upgrade path) it was multistore (3 stores, 3 domains, over 10k products all on one backend admin with custom made extensions plus Me2PRO integration for ebay as well).
I can configure your linux server as well such as apache, php plus optimize mysql for maximum performance). Let me know if you interested, the reason why i bid a little bit higher than other is i know that magento upgrade can be tricky and maybe mysql conversion will be required all depends on your setup.
Upgrade from 1.9.1 to 1.9.2 required custom cache script which i can develop for you.
(it is for baypass magento bug, half of dev on your bidding list don't have a clue)
I can migrate all bunch of your extensions one by one and if any rewrite will be required i could do it.
You pay only when final product is delivered and tested.
Also i can develop or rebuild existing modules, but before we start i need more info regarding your setup etc (version, platform,,,,)
I could provide support during the migration and after if required.
If you want to see some of live websites in action please let me know and i could do small presentation to proof there are not an empty words.
Kind regards
Chris