So it's ADSL.
IPStream Max = "up to 8Mbps, with rate adaption et al".
You
do mean 250 kilo
bits per second as in home250, yes?
Look at the FAQ for an explanation of SNR, and look at whatever kit you've got already. You
might be able to extract an SNR (Margin) from it (somehow, there's instructions for some devices in said FAQ) - if it varies significantly over the course of 24 hours, you
might have issues.
If home250's all you can get, then there's a good chance your line's marginal as it is.
Huh?