Have I Hit The Point Of Diminishing Returns?

A thought to consider: Rather than fixing what doesn't seem to be broken (i.e., "upgrading"), consider adding a high quality pair of headphones and a headphone amplifier. I find having both speakers and headphones available (Stax electrostatics, in my case) to be nicely complementary. For several reasons:

1)Having two (very different) sonic perspectives adds interest from a musical standpoint.

2)Headphone listening takes the room, the speakers, the power amp, and most of the preamp circuitry out of the picture (assuming the headphone amp is connected to the preamp's tape outputs), which can be helpful in diagnosing system issues and/or providing reassurance when audiophilia nervosa strikes.

3)Headphones, of course, can make it possible to listen when listening via speakers would disturb others in the household.

Just a thought. Regards,
-- Al

07-27-14: Rlb61
Interesting views. My power amp is 225 wpc dual mono, so I THINK it's powerful enough, but I could be wrong.

For B&W speakers it's not only about Watts/ch - it's about how much current the amplifier can provide to this particular brand of speakers. B&W are well-known to love high-current amplifiers.
I searched hard on the internet to find some A300CR specs but all I could find was A300 & A3CR specs. In particular I was trying to back-calculate the size of the A300CR transformer & the amount of current it could provide.
B&W speakers have a terrible impedance & phase curve in the low freq which gives most amps a lot of trouble because the amp is forced to output a lot more current than what the impedance-only curve informs you.
If you look at purely watts, you might be OK but you probably are shy on output current & that might be limiting you. FWIW.

Bombaywalla - Here are the specs from the manual:

225 wpc into 8 ohms

THD @ 100watts, 1 kHz < 0.005%

Frequency response - 10Hz- 20 kHz +/- 0.1dB
10Hz -100 kHz +/-1.5dB

Channel separation - Immeasurable - below noise floor

Input sensitivity - 1400mV for 225 watts output

Input impedance - 31 kOhm

S/N ratio ref. 225 watts output - > 110dB unweighted
> 120dB 'A' weighted

Power consumption - 1150W Max

Your help on this would be most appreciated. Thanks.

Thanks Rlb61.
I surfed the web last night again to see if I could get some dope on this amp but it was hard to find anything. So I'm still guessing at the input power transformer size.
Looking at the A300 amp profile I'm thinking it's a 1KVA transformer.
if so, then, I calculate something like 11Amps/channel. Further, you have the plus & minus rails so each rail gets 5.5Amps. That's a very low amount of current to make a floor-standing B&W really sing. You'll get pretty OK sonics using such an amp but the speaker is capable of much more which could be unleashed by using an amp that has a 2KVA or higher power transformer (which would double the current output). Now you are talking of an amp that it pretty tall - like 10" tall - and much more expensive.
Class-D amps get you high current in a smaller chassis & for fairly reasonable price.
Unfortunately, that's the nature of the (B&W) beast.

one serious thing to consider is to passive dual-amp (I'm not using the term bi-amp as bi-amping implies xternal x-over) using a high-current, low-impedance capable, reasonably priced class-D amp to drive the bass (you've biwired them so they have 2 pairs of binding posts). Then, 225W/ch of the A300CR should be plenty for the highs & mids. FWIW.

Bombaywalla - Thank you so much for your effort and advice. It is appreciated greatly.