Yes, that's bad, you don't want a loop on either power or ground. Break both loops somewhere so that you have a C (or Y) shape. Never a loop. It would also be best if it was broken such that the left channel was on one branch and the right channel on the other to reduce cross talk through the power trace impedances.
The reason you don't want any loops is that they will couple enourmous amounts of electromagnetic interference onto your power supply rails since you've built a loop antenna. This is mostly high frequency (near RF) and bypass caps do absorb a lot of it. However on your layout I only see big caps which will do little or nothing to attenuate RF noise, you'd need to throw in some low value ceramics in parallel to do that (0.1uF ~ 1uF).
At lower frequencies (audio) the loop doesn't respond so much to EM fields like an antenna but rather directly to just the alternating magnetic field. Acts like a really crappy transformer. This will generate time varying potential differences all along the loop proportional to the external field. Pretty much anywhere in your house there is a strong 60Hz power line field and a rich set of harrmonics pushing well above 1kHz. Power and ground loops beg for an amp to hum. If everything is just right, your ears are good enough, and your TV sucks you can also be treated to 15kHz vertical sync interference. Most amp's power supply rejection ratio drops quickly with frequency, so even though this signal may be lower than 60Hz power line noise the amp is more susceptible to it.
Of course, you can always build the amp as is and if you have an interference problem cut the loop by hand. But you aren't really buying anything with the loop and its trivial to break now, so I'd do that.
