Unable to startup with USB Hub connected

I've been having a problem lately with my iMac 27" (Late 2013) getting passed the startup chime while my 10 slot USB Hub connected. Connected into the hub is 6 external hard drives, an external Blu-Ray drive, Lightning to USB cable, and a USB extension cable that goes into one of the powered slots that I use for misc. devices. For the most part, it just takes my iMac a while to startup when it works properly, but every now and then, it won't startup properly at all until I startup with the USB hub disconnected. So here's what I'm wondering:

1. Should I look for a USB hub that has 10 powered slots, or does one even exists?

2. Is there something I can do to make sure this doesn't happen, because I do need that many USB devices connected at once, at least the 6 drives.

3. Is there such a thing as USB hub that connects to a Mac via Thunderbolt instead of USB?