Pix 501 will do about 50m clear, so long as you aren't running fix up rules, or cookie blocking and http inspection.
If you are running it as a VPN endpoint, its 3Mb/s 3DES and 3.5Mb/s AES.
Bear in mind they come with either 10 or 50 concurrent connection limits (i.e. open connections) so are not the best thing for sticking P2P behind...
If you need anymore help, drop me a PM as I don't come in AAISP often.
Also the 515 being the fail-over depends on which license is installed as to whether its recoverable to a stand-alone primary, BTW and seems to be a bit of an overkill for home use!
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Happily bonding ADSL lines with
Xifos at 26Mbps
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