You may want to consider stepping up on all three:
V6R1 to i7.1
V7R126.96.36.199 to V7R7.4
EM320 to EM350
On these last two - you're getting down towards a pinch off of support.
You're already at the point where you have to stagger upgrades.
First step: Upgrade your HMC from V7R3.3 to V7R3.5
Second step: Upgrade your firmware from EM320 to EM350
Third step: Upgrade your HMC from V7R3.5 to V7R7.4
Staying current on firmware will:
- ensure you can put on hardware that needs it with less downtime at the
time you need it catching up on firmware
- be ready for OS upgrades which may require new firmware
- if your HMC fries and IBM has to air you a new one preloaded at a higher
level of HMC code you're ready to go.
- Take advantage of fixes and security patches
Staying current on HMC code will:
- allow you to use newer browsers which may poorly render prior levels of
- Get the best of experiences with remote connections and what not
- allow you to use latest firmware (see above)
- if your power 6 suffers catastrophic hardware loss and needs replacing
you'll have a hmc ready to go at the latest firmware level.
- Even if just your FSP needs replacing it may come preloaded at newer
- Take advantage of fixes and security patches.