multiple 3com superstack II switches

Why use a crossover cable? use an Uplink port.
Anyhow I dont know of any bottlenecks for the 30 feet.
I use the allmost the same seup 3 switches connected with about 10 feet runs.

The only issue to using a crossover cable vs the matrix cable is the best you can get via category 5 in a "vanilla" 3300 is full duplex 100mps, so in theory, this one switch is going to be less capable than the other two.

A matrix module/cable gives you almost a gigabit connection.

Depending on the model of 3300 you own, you can get an optional fiber or Cat-5 Gigabit transceivers to connect the two.

I don't understand why the separation of 30ft. Is it a physical limitation of your existing cabling or?

We use the same switches on our LANs. There is a limit to the length a matrix cable can be, and I believe it is only about three feet. The maximum distance you can have for a crossover cable between two switches is about 100 meters. 30ft (about 10meters) is well within that range. I wouldn't worry too much about a bottleneck on the crossover. 3 3300 switches have a total of 72 ports. With that few nodes on your LAN, you would notice no difference between a crossover or matrix cable.

Formore detailed info, check this 3Com web page:
http://support.3com.com/infodeli/tools/switches/s_stack2/1698-5/manual.a01/index.htm (there should be no spaces in this link).

If I am not mistaken the 3Com 3300 has one expansion slot. You can fill this expansion slot with
- 100 BaseFX Module
- 100 BaseFX Dual Module
or even Gigabit over UTP or Fibre.

However this is not a cheap solution. If you use cross-cables you will lose a port and have a major bottleneck. My experience is that the Gigabit Modules do the job. I choose the UTP-module purely based on price.