Given your wanted Ad on the classifieds then a s/h kona kula frame would not be a bad choice if you could find one.
The Supreme (scandium tubed) is the full on race orientated one with the steeper HT whilst the other models are a bit more trail oriented with a slacker HT but still very light. A Supreme may be a bit over budget but the Primo and Deluxe frames would be nearer your price mark
I had Maxlight XC briefly and really loved it, then replaced it with the Kona which I also really liked – bit of stiffer ride than the Maxlight despite being the same Easton Ultralite tubing. My 17in Kona Kula frame was sub 1.5kg
Otherwise s/h a Giant XTC frame – cheap as chips?