Yes it will help to get the upgrade. But no guarantees.
Not sure of the amount it will increase each thing.
But, things that should help out that cost nothing:
1. Use a PS driver, it will vastly reduce the spooled file size over PCL, Generically speaking averages, with a PS driver it multiplies size in the spooler by a factor of 10, so a 4.5 MB job would likely spool to 45MB. PCL could very easily more than double that.
2. Make sure the networked port is LPR , queue name is lp and LPR Byte Counting/SNMP are disabled
With those settings I would think the jobs should go through fine up to a file size of 100MB assuming fonts and images are embedded properly in the file.