I'm looking for something low-cost and reliable with 10+ SATA ports for expansion. Can anyone name some widely available components for this purpose? Lowest cost is best. Thanks.

...have a look at these models: http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007623%20600035108&IsNodeId=1&bop=And&Order=PRICE&PageSize=20

 

...quite some power, with embedd SB celeron, the price is hard to beat.

 

You need to check what PCIe slots are available...I'd prefer this one: http://www.amazon.com/MSI-7835-001R-C847MS-E33-Mainboard-mATX/dp/tech-data/B00B4M33WA/ref=de_a_smtd

 

...controller: http://www.newegg.com/Product/Product.aspx?Item=N82E16816101358R

If you get a motherboard with 6 sata ports and a couple PCIe slots, you can add 4 more ports to get your ten with a couple of these ~$12 sata2 cards from monoprice:

http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10407&cs_id=1040702&p_id=2530&seq=1&format=2

 

Several comments there confirm they work with unraid and I just installed one this week with no issues.  At the very least, they are a good stopgap until you need an 8-port HBA.