It's 2X the $400 you stated, but the Parker Tornado I just bought has been a sweet shooting set-up. Light, dead on consistent accurate and apparently plenty fast enough. I am 6 for 6 with it out to about 42 yards.

Be very careful. Some of the less expensive models cut corners that end up being a real mess. I saw one model that was priced around $400 that used a Teflon tape strip rather than a quality cable slide (not the rail, but the cable crossing). After 50 or so shots, the tape was essentially gone in places, and rolled up in others. The wear on the cable rendered the set-up essentially unusable.