4 - Hartke 2.5XL's stacked in 2 vertical arrays (on end) here. However, amp rack is comprised of 2 Alembic F2b preamps, MXR Dual Limiter, and Crown XTI1000. I like the tight bottom end and crisp mid-top end of Hartke 2.5XL's on vintage stereo Rickenbackers. (Pics when I get them.)