So would getting a 10 gb nic for each 4300 really help out with performance to and from the SAN?
Not really something that can be answered with the sparse info provided.
I'm generally skeptical in cases like this that bandwidth alone is the issue. The metrics you should monitor are throughput, IOPS and latency.
Depending on disk type, number and RAID mode (provide these infos), you can stress your disks with a lot of small and random IOPS, which naturally uses low bandwidth that even 100 Mbit/s links can cope with easily, but high latency and poor performance since the physical disks are the bottleneck.
First of all you should make sure to use Round-Robin IO if your SAN supports it in order to use multiple paths. That alone should increase your available bandwidth a fair bit at no additional cost or configuration requirements.