I doubt that is the problem - if the loco plus sound card was trying to draw more current than the controller can output, then the overload cutout should trip and nothing would work at all. If the loco is running but is still without sound, then the problem is going to be somewhere in the sound card or its wiring.
Having said that, if you want a more powerful controller anyway (which you'd need if you get any 2-motor locos, or one that is more power-hungry than LGB types), you could look for a bigger LGB one second-hand (2 amp or 5 amp), or go for something like a Helmsman unit, British-made with lifetime warranty and highly recommended by a number of folks on here who run analogue.
Jon.