Basic computing and 6+ PCIe slots don't really mix. Here is the "cheapest" available build. And honestly there is a lot wrong with it in terms of a balanced system. But if basic computing power is all you need, this can do it and give you the PCIe connectivity you wanted.
Chances are you don't have a similar size/style computer laying around to swap parts with.
PCPartPicker part list: http://pcpartpicker.com/p/zdYJBm
Price breakdown by merchant: http://pcpartpicker.com/p/zdYJBm/by_merchant/
CPU: Intel Xeon E5-2603 V2 1.8GHz Quad-Core Processor ($206.98 @ SuperBiiz)
CPU Cooler: Cooler Master RR-T4-18PK-R1 70.0 CFM Rifle Bearing CPU Cooler ($14.99 @ Newegg)
Motherboard: Asus P9X79-E WS SSI CEB LGA2011 Motherboard ($464.98 @ SuperBiiz)
Memory: Kingston Fury Black Series 8GB (2 x 4GB) DDR3-1600 Memory ($74.99 @ Amazon)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($53.98 @ OutletPC)
Video Card: EVGA GeForce GT 620 1GB Video Card ($45.98 @ Newegg)
Case: Rosewill RISE ATX Full Tower Case ($85.00 @ Newegg)
Power Supply: EVGA 850W 80+ Bronze Certified Semi-Modular ATX Power Supply ($69.99 @ Newegg)
Optical Drive: Samsung SH-224DB/RSBS DVD/CD Writer ($14.99 @ Amazon)
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-09-05 13:32 EDT-0400