Switch stack layout, MPIO, multiple subnets

Hi All,

I hope you all can give me some advice with the following.

Currently we have the following setup:
- 2 x Cisco 3750G switches configured in 1 stack
- 2 x EQL PS6000 E connected redundantly to both switches
- 3 x EQL PS6000 XV connected redundantly to both switches
- Several Dell R710 with broadcom 5709 ESXi vSphere 4.1 hosts (4 ports connected with one virtual switch for SAN, connected redundantly to both physical switches)
- Several Dell R710 with broadcom 5709 member servers (2 ports connected redundantly to both switches)

Now our problem: We dont have ports available on the switches anymore and if we need to perform maintenance on the switchstack all storage will loose its connection.

I can do two things:
1. Connect two extra 3750G's to the switchstack
2. Create an extra switchstack of two 3750G switches, create a portchannel between both switchstacks of 4 or more ports per switch to guarantee bandwith.

For option 1 I instantly get extra ports but I still cannot perform maintenance on the switchstack without affecting the storage and maybe I get a certain overload on the stacking cables when adding additional arrays or servers/esx hosts?

If I go for option two I have to use 2 subnets I believe? Is this correct?
If so then these subnets should be routable right? to make sure that all equallogic and their interfaces can communicate with each other. So all traffic between the two subnets are going trough our router and this creates latency's and bandwith issues between the ISCSI switches and our core network equipment that isnt acceptable.
Also I read in the config guide of the equallogics that if you want to use MPIO you need to have both interfaces on a member server on the same subnet, but I want to devide all connections on my iSCSI san over both switch stacks.

So I am a bit confused on how to continue with expanding the iSCSI network.