Having a 1mbit line or more won't affect ping to any great affect (not over a 512kbit line at least) but it will give you approximately /10 per second downloads.
So, a 1.6mbit line can allow you to download up to approximately 160k per second, 1.6 mbit = 160kbytes (bloody fast). This is simply taken from the formula that every byte is made up of 8 bits of information, with 2 bits between each byte as a spacer. So you have 10 bits for each byte.
Remember, though, that download rates are always capped by the source's upload rate, so if you're downloading from a 56k line you'll still only get 5.6k max download per sec.
Wish we could get 1mbit+ lines for that kind of price here...
In the UK, for a 512k DL and 64-256k upload line, it costs a minimum of £26.99 (or thereabouts). Mine costs £29.99 with 50 mbs webspace. That's approximately $50 a month.
Mind you, pings in this country are always awesome so it's kind of worth it if you're a gamer. I've actually seen my ping go down to 1 once
