I'm thinking about buying a few Homplug AV 500 network adapters for use in my home, but I've noticed that the cheaper ones tend to have 10/100mbit ethernet ports, rather than gigabit ports. The price difference is large too - the gigabit port ones seem to cost about double the 10/100 ones. My questions are:

1) Given that the adapters are theoretically capable of 500mbs transfers (I know it's almost impossible to get anything like that speed in the real world, of course), would a 10/100 port constrain the speeds of a 500mbs adapter? I'm kind of assuming it would, otherwise why sell 500mbs adapters with gigabit ethernet ports?

2) So if it does limit transfer speeds, by how much? What are the 'normal' achievable transfer speeds across Homplug 500 adapters with gigabit ports?