I would have to again disagree with you...you shouldn't have been using 10g anyway, the smallest gauge you should go is at least 8 when grounding subs. But in your case of talking about radioshack you would be right since they do not carry this thick wire. But keep in mind that your car ground is only around 8 gauge so to ground bigger than that would be pointless.

Unless you are running a 2000+ Watt system and then we can talk differently.