Just a quick addition to Ron's
Keep in mind that a single flow will only use a single link, but in aggregate among multiple flows, you will get the full bandwidth of the aggregation
2910al switches use simple IP source-address/destination-address (SA/DA) traffic distribution, so all frames between the any two IP endpoints always use the same port combination (for each direction).
Since that distribution is rather random it'll only provide proper load balancing with a larger number of endpoints (or fine-tuned addressing). If that doesn't work out you might need to add 10G modules.
Also note that it doesn't matter speed-wise whether you use twisted-pair copper or SFPs with fiber. Fiber just enables longer reach.
Additionally, "stacking" with the 2910al just means management through a single IP - you can switch the chassis in CLI or the menu. It's not a true stacking in the sense of both switches acting as a single one.