A bit of info relating to the 6060:
Firstly, it was UK manufactured (or at least I know the European market ones were). Creek have gone to chinese manufacture these days (like everyone else) but the 6060 was built way before then.
The 6060 (like it's little brother, the 5050) was designed and made during the period that Mike didn't own the company (1988-1993), when it was owned by TGI Group. Mike was still involved in the design so I understand. As far as I know, Alex Nitkin was only employed later, after Mike bought the company back. Alex was certainly involved during the much later original 53 series models.
I've had two 6060 and probably three 5050. They are both nice amps (particularly the 6060) but then I've not heard a Creek that I didn't like. Never seen a far-east market one like yours though. If you want a 'translation', I might still have a picture of the back of one of mine.
It shouldn't struggle to go loud on a normal speaker load so it might suggest that there is indeed an issue depending on the test impedance.
One of the switches on the back puts it into bridge mode though for driving a single channel so check that's not pressed. No idea if trying to drive two speakers in bridge mode would give you the symptoms you have?? Anyone?
Geoff