I've just had a new laptop built by www.pcspecialist.co.uk - it was especially for music production and live use...
It's a 17" i7 (not over-clocked, no real need for audio) running at 3.4GHz, 16Gb RAM, 1Tb hybrid hard disc with 128Gb of solidstate, with bog-standard sound card (no need for fancy sound card if it's always running into a Focusrite). All for £700 inc wireless mouse.
And it's quick - I'm into an Ableton project within 20 seconds of switching on, and much of that time is typing in my pass word!
And so far had no glitches or track dropping, even at 32 tracks all with up to 5 VSTs...