I second StockingsHQ, it's great. My favourite everyday stockings on there are the Transpereze Sara ones, partly because at 20 denier they're a lot tougher then 10 and 15. They don't seen to do an equivalent in hold-ups, but there are some 20d hold-ups from other brands on there.
If you tend to rip them at the toes, make sure you're getting reinforced toes. If it's the heel, have a look at the RHT section.