PE2950 Upgrade system backup

Hi all,
I want to update my backup system by adding an additional external drive LTO4.
Currently the system is composed of:

Dell PowerEdge 2950
Dual CPU: Intel Xeon CPU E5440 @ 2.83GHz
RAM: 8GB
Controller HDD (RAID1 + RAID5): PERC 6/i Integrated
Controller Tape Drive: Adaptec ASC-39320A U320
PV110T with two LTO3 Tape Drive
OS: Windows Server 2008 R2

 PV110T Dual LTO3 Tape Drive

Whats the difference between PVLTO4-120 and PVLTO-4-120 HH?
Which one is the best for my system?
Having to install an additional SAS controller card for connection to the external LTO4, can I have problems?

I am sorry, but English is not my language.

Have a nice day.
Maury