if it were me, and budget was not really an issue, i'd go for a Digital Designs C4.
http://www.ddaudio.com/dd/amp/C4.asp
it'll provide 2x70wrms for you splits, and 1x420wrms for your sub.
also, when you eventually upgrade, you can use it to power an active front stage (has bandpass feature), and purchase a separate monoblock for sub duties (e.g. DD M1)
the C4 is a bit pricey at $799-RRP though.
a budget option would be a Jaycar 4x100 amp, which provides 2x130wrms + 1x380wrms. only $299 too
- Stooge007 out