I am on alamy as well, but I don't think there is a need for total switch over.  Pictures that you took which are very specific location, or copyright material, or newsworthy may sell better on alamy.  However talking about the micros.

Shutterstock is a no brainer.. submit to them
Istock.  They have good earnings but I find it fairly laboursome to submit too.  I still submit, but I grumble every time.  I also find the 20 image/day upload limit a pain.
Dreamstime- they have been good.  not as good of a $/picture/year as Istock or shutterstock (which are about the same) but I have good income from them
Bigstock, and Fotolia - they are about the same in earnings. Bigstock is a little easier to upload to I think, However Fotolia gives the .20 per accepted image which ads a fair bit.

I also submit everything to stockxpert and 123RF.  Stockxpert takes 0 work to submit to... it is just a matter of letting your ftp uloader fun, then click 1 button to submit the 200 images you just uploaded (if you have embeded keywords and titles)... very simple.  123 RF is almost as easy as they don't have any catagories.... so i find uploading to them is generally well worth my time, despite the low earnings there.

I don't submit to feature pics... I haven't heard of much action there.. but if you hear different, I would be interested in knowing.