Hi all,
I am looking for a MIDI controller keyboard to use with Sonar X2 and its various ACT functions and am considering the Roland A800 or A500.
Now I know that these keyboards can be powered via a USB port or can be independently powered through a PSU.
I have a Dell laptop with only 3 USB ports: One of these is already used for an external SSD and one is used to power an Edirol UA-25. That leaves one port free for a controller keyboard / other.
Question I have is this: Is there a difference between using standard MIDI cables between the controller keyboard and Sonar, and using a USB cable? Is it possible to use a USB splitter and connect up the controller keyboard along with say, a mouse or other input device? I'm not sure if using a USB splitter will affect the power supplied to the keyboard and whether this would be supported.
Any ideas?

The A-Pro PDF manual says using a USB hub could cause some problems (installation failure, clicks, dropouts, etc.)
I have 4 USB ports that are occupied with an A-800Pro, Quad-Capture, external hard drive (when doing a backup task), and iLock. I use a wireless (bluetooth) mouse and keyboard. Perfect.

Connecting the A-Pro using a MIDI cable (instead of an USB cable) won't give you two separate ports (A-Pro 1 & A-Pro 2), which will be problematic, I think.

OK - that's useful information regarding the (non)-use of a USB hub. Thanks.

Coming back to the question about using a standard MIDI cable v USB cable - I don't understand what you mean with regards to having two separate ports. Looking at the documentation, I will have a standard MIDI OUT port and a standard MIDI IN port. I want to know whether Sonar's ACT functions will map correctly using standard MIDI.

When A-Pro is connected to a PC via a USB cable, Sonar's MIDI device page shows these ports:

<Input Port>
A-PRO MIDI IN
A-PRO 1
A-PRO 2

<Output Port>
A-PRO MIDI OUT
A-PRO

P.23 of the Owners Manual downloadable from the below link explains about these ports, and it says that the A-PRO MIDI OUT "Transmits MIDI messages to MIDI devices connected to the A-PRO’s MIDI OUT connector" but does not mention the A-PRO sliders, knobs, etc., which you want to control using ACT. So, I think it's not possible with just a MIDI cable.
http://www.rolandus.com/support/search/A-800PRO

To check this, I connected my A-800PRO and my audio interface (Quad-Capture) using a MIDI cable and deselected the A-PRO 1&2 ports from Sonar's MIDI device page, but for some unknown reason Sonar wouldn't receive MIDI messages from A-Pro (via Quad-Capture) when I play the keyboard, although I select "All Inputs" from the MIDI track's input pull-down menu. Maybe I have to change some setting in A-Pro or Quad-Capture, I don't know.

So, I highly recommend using a USB cable and use those 2 A-Pro ports. Also, without a USB cable you'll have to use an AC adapter.

Sorry, I couldn't help much. A-Pro's ports and the ACT feature are still bit of a mystery and I don't fully understand them. 

Thanks for the reply Jlien X. In any case, despite the unknowns with the way the A800 behaves when using standard MIDI, I have raided the piggy bank and bought one. If I find that my laptop is too restrictive in terms of I/O & USB ports I guess I will have to go on the upgrade path (again!)