If it's an SX crack, it's likely to crash anyway. If it's a Waves crack, and an SX crack, then crashes are very likely indeed. If it's SX1, that's a lot less stable than SX3.
But don't pay 350 quid for SX. Pay 99 for Cubase SE. You really don't need all the stuff that's in SX -- surround etc. See
http://www.dv247.com/invt/29688/ for features and pricing. It's got:
* 48 Audio tracks and unlimited MIDI tracks
* Professional 24/96 recording
* Up to 16 VST instrument slots
* 5 insert effects and 8 send effects per channel
* VST System Link and ReWire 2-compatible
* VST audio and MIDI plug-ins included
* Video thumbnail track for building your own video soundtracks
* Technology and user interface based on Cubase SX3/SL3
* Fully automatic delay compensation for plug-ins
* Enhanced user interface (same “look and feel” as Cubase SX3)
* Improved Hitpoint detection for tempo adjustments of audio loops
And so on.
I wouldn't go the Logic route personally because I think it's over-complicated, but the full version has fantastic plug ins and many people do love it to bits. There's a cheaper version of Logic as well for 169 quid.
http://www.dv247.com/invt/27714/
Or, you could get Reason, which will get you up and running a lot quicker, but will cost you three hundred notes.
Pays your money and you makes your choice. Reason would be best in terms of actually getting stuff done -- your biggest cost isn't your software, it's your time.