Jose wrote:

...
The 308's would go as low as around 37 Hz, also for Yamaha I suppose, that then still leaves a lower gap of around 10Hz, strictly speaking.

Not really.  There is hardly any energy below about 50Hz in the piano's sound. 

This explains how it works.

and see this if you still need convincing.

Hi,

I just added a ESI 10'' subwoofer to my KRK 5 monitors. And I must say it makes a difference to me. Could I live without? - yes.

But a sub does not only jump in for frequencies <40Hz. You configure the crossover frequency for the lower and upper end. The low-passfilter (defines at which lower frequency the sub starts working) and high-pass filter (above which frequency the monitors start). In my case I set the monitor Crossover freq to 100Hz and the Sub to 120 HZ. So the Sub contributes from 120Hz downwards.

Although the Monitors go down to 45Hz, the response in those low frequencies is not as good as in higher frequencies. I think frequency response curve is the keyword here.

When the big box arrived at home I told my wife "It has a 30 days return option! Maybe you are lucky and it doesn't make a difference". Three hours later I told her that I won't execute the option.

So, I feel the difference. May it be very subjective but the vibrations at my trousers are not.

Bernd

...
The 308's would go as low as around 37 Hz, also for Yamaha I suppose, that then still leaves a lower gap of around 10Hz, strictly speaking.

Not really.  There is hardly any energy below about 50Hz in the piano's sound. 

This explains how it works.

http://en.wikipedia.org/wiki/Missing_fundamental

and see this if you still need convincing.

https://www.youtube.com/watch?v=5xjD6SRY8Pg

hi all,

I am about to buy the stuff I need for my new software modelled piano. After doing my research I decided to go for the Kawai VPC1 (I don't suppose there will be a VPC2 anytime soon), a Presonus audiobox 22VSL interface, and JBL LSR 305 monitor speakers (and Pianoteq Standard).

I have high quality components but was wondering whether I need to worry about the quality of the XLR cables as well or will a pair of standard cables do?
As for the lower frequencies, the monitors go to  around 42 Hz, this would suggest I need an additional subwoofer for the lower frequencies, but I am not sure I would need the extra punch, I could buy one later but what is your experience?
Thanks.

The Presonus audiobox 22VSL has balanced jack outputs.
I recommand you 2 balanced (TRS) 6,3 jacks for the best result. The XLR won't give better result. Quality cables are always a good investment.
For the need of a subwoofer, I don't know.
But, IMO, you should consider the Yamaha HS7 that are 6,5" instead of the 5" JBL.
They cost a little more but these 6,5" should have enough bass to prevent you from the need of a subwoofer.

I am about to buy the stuff I need for my new software modelled piano. After doing my research I decided to go for the Kawai VPC1 (I don't suppose there will be a VPC2 anytime soon), a Presonus audiobox 22VSL interface, and JBL LSR 305 monitor speakers (and Pianoteq Standard).

I have high quality components but was wondering whether I need to worry about the quality of the XLR cables as well or will a pair of standard cables do?
As for the lower frequencies, the monitors go to  around 42 Hz, this would suggest I need an additional subwoofer for the lower frequencies, but I am not sure I would need the extra punch, I could buy one later but what is your experience?
Thanks.