Eug
Lifer
CAT3 is not spec'd to support even 100 Base T.think about the folks that did cat3 when it first came out - They might be able to do gigabit with very short range and alot of retransmits - no chance in heck 10gb - and what is your option? rip it out.
CAT6 is spec'd support everything all the way up to 10 GigE, at least to about 120 feet, and more like 180 feet.
I have a very large home, and not a single run anywhere in the house is longer than 100 feet.