We have been shooting 300-600yrds and want to extend this to 800-1200 and i have an opportunity to obtain a Leupold scope at a good discount. Thinking about the Mark 4 6.5x20x50 - can't afford to go much above that - maybe the 8.5x25. Or should I go for the HDMR or PST any thoughts. Currently using a Muller 8x32 and any heat waves kill it quickly.