Kclone,
you can get some hints from various aspects but in the end you will have to do some math to determine whether or not the power amp is capable of high(er) current.
As Jmcgrogan2 stated one aspect is sheer weight of the amp. This assumes that the weight is from the power transformer & the power supply caps. As Kijanki pointed out w.r.t. the Rowland 625 class-D power amp, you could be totally fooled with the weight of this amp; it's all in the chassis & the class-D power supply is compact & relatively light weight! So, obviously ensure that the power amp you are looking at is class-A, class-A/AB or class-AB.
As Jtcf pointed out - another aspect is wattage specs. does the manuf list the wattages for 4 Ohm, 2 Ohm & 1 Ohm. If yes, do the wattages double each time the speaker load halves? If it does most likely the power supply is very robust & can provide gobs of current (Gryphon Audio amps are often spec'd down to 1 Ohm, doubling wattage for each halving of speaker load impedance. BUT.....they DO cost a bomb! ;-) Comes with the territory) If the wattage does not double per each half of the speaker load, the power supply is robust but not that robust. I know this is a fuzzy statement so it has to be dealt with on a case-by-case basis. A power amp wattage might double for 4 Ohm load & then might go up 30-40% for a 2 Ohm load. This should tell you that a 2 Ohm load for this amp is going to be a burden & that it can support upto a 4 Ohm load quite well.
Yet another aspect is to look at the amount of power supply decoupling capacitance. Just a blanket statement here - the more, the better. Of course you cannot have any power transformer with any current capacity hooked to some arbitrary amount of power supply decoupling capacitance. It takes a large amount of charge to tank up those power supply caps hence the transformer's got to be up to the job otherwise it will hurt the dynamics. Considering that the correct transformer is used, if one has more power supply decoupling capacitance the power amp is better able to supply load transients & maybe even a short burst of current into the output stage.
Related to this the type of power supply capacitance - do they look like coke cans or do they look like a 35mm film roll. Most manuf today are using caps that lool like a 35mm film roll & many, many of those in parallel. They say that it's better for dynamics. They do have a point here - the ESR of the many parallel caps are all in parallel which means that the net ESR is small. Small cap ESR is a good thing for swift response from the power cap. OTOH, tho', the inductance of the cap leads & the physical distance of the furtherest cap from the amp output stage can add series inductance to the overall capacitance & this is not a good thing for swift response from the power cap. The other thing I don't like is that all the dozens of small caps used might not age the same way meaning that the load is not shared equally by all the caps in the array. Also, it's very likely that 12 or 20 parallel caps take up more real estate than just 2 coke can caps.
One method I like to ascertain whether a power amp is high current capable is hinted by Marakanetz - I try to find out the transformer VA rating & also the secondary AC voltage rating. By dividing VA by secondary AC voltage rating you get the current handling capacity of the transformer. Divide this current by 2 - since we have a left & right channel. Of course, no need to divide by 2 if the amp is a mono block. This is the max current the amp can output per channel no matter what the (gibberish) spec sheet says. Higher current is better esp. if you are trying to drive a difficult speaker load.
Hope that this helps. FWIW.
you can get some hints from various aspects but in the end you will have to do some math to determine whether or not the power amp is capable of high(er) current.
As Jmcgrogan2 stated one aspect is sheer weight of the amp. This assumes that the weight is from the power transformer & the power supply caps. As Kijanki pointed out w.r.t. the Rowland 625 class-D power amp, you could be totally fooled with the weight of this amp; it's all in the chassis & the class-D power supply is compact & relatively light weight! So, obviously ensure that the power amp you are looking at is class-A, class-A/AB or class-AB.
As Jtcf pointed out - another aspect is wattage specs. does the manuf list the wattages for 4 Ohm, 2 Ohm & 1 Ohm. If yes, do the wattages double each time the speaker load halves? If it does most likely the power supply is very robust & can provide gobs of current (Gryphon Audio amps are often spec'd down to 1 Ohm, doubling wattage for each halving of speaker load impedance. BUT.....they DO cost a bomb! ;-) Comes with the territory) If the wattage does not double per each half of the speaker load, the power supply is robust but not that robust. I know this is a fuzzy statement so it has to be dealt with on a case-by-case basis. A power amp wattage might double for 4 Ohm load & then might go up 30-40% for a 2 Ohm load. This should tell you that a 2 Ohm load for this amp is going to be a burden & that it can support upto a 4 Ohm load quite well.
Yet another aspect is to look at the amount of power supply decoupling capacitance. Just a blanket statement here - the more, the better. Of course you cannot have any power transformer with any current capacity hooked to some arbitrary amount of power supply decoupling capacitance. It takes a large amount of charge to tank up those power supply caps hence the transformer's got to be up to the job otherwise it will hurt the dynamics. Considering that the correct transformer is used, if one has more power supply decoupling capacitance the power amp is better able to supply load transients & maybe even a short burst of current into the output stage.
Related to this the type of power supply capacitance - do they look like coke cans or do they look like a 35mm film roll. Most manuf today are using caps that lool like a 35mm film roll & many, many of those in parallel. They say that it's better for dynamics. They do have a point here - the ESR of the many parallel caps are all in parallel which means that the net ESR is small. Small cap ESR is a good thing for swift response from the power cap. OTOH, tho', the inductance of the cap leads & the physical distance of the furtherest cap from the amp output stage can add series inductance to the overall capacitance & this is not a good thing for swift response from the power cap. The other thing I don't like is that all the dozens of small caps used might not age the same way meaning that the load is not shared equally by all the caps in the array. Also, it's very likely that 12 or 20 parallel caps take up more real estate than just 2 coke can caps.
One method I like to ascertain whether a power amp is high current capable is hinted by Marakanetz - I try to find out the transformer VA rating & also the secondary AC voltage rating. By dividing VA by secondary AC voltage rating you get the current handling capacity of the transformer. Divide this current by 2 - since we have a left & right channel. Of course, no need to divide by 2 if the amp is a mono block. This is the max current the amp can output per channel no matter what the (gibberish) spec sheet says. Higher current is better esp. if you are trying to drive a difficult speaker load.
Hope that this helps. FWIW.