S4 and Maschine

Hi,

So i finally was able to afford a 15" MBP and iMac, both purchased this year and thought my audio headaches would be over coming from a Windows environment, not so.I've been wanting to do so much with what i have but even both Macs are giving me issues...When i launch either app by itself it behaves, audio is good.However i recently tried to sync via MIDI the Maschine and the S4 and with both apps open i get dropouts and bad sound, especially from Maschine.Launching both apps gives me bad audio...why?? i thought Macs could handle this ??
Could it be a USB issue?
I also have two Kontrol F1's, so with Maschine and S4 that means 4 USB devices plugged in and because the MBP only has 2 USB ports i purchased a high end USB 3.0 hub with AC power.I connect all NI devices on there and my 1tb external goes into the other USB port on the MBP.I leave it like this when i use my iMac also (iMac is for home use and MBP is for outside use) because it's easier than unplugging all NI products when switching.
Both Mac's came with standard stock (MBP 4gb ram, iMac 8gb ram)

Should i buy an external USB soundcard like the A10?

I'd really like to resovle the issue with what i have.

Any help or guidance would be appreciated.

Thx !!