Hi akWolf welcome to the forums
If your looking for a 5 bay enclosure keep your eyes open on Newegg puts them on sale for around $130 about once a month of late. The most common enclosure used here are the Sans Digital TR5m http://www.newegg.com/Product/Product.a ... 6816111166
The TR5m has a couple of versions the one above uses an eSATA connection but there is a USB version and another that offers both USB and eSATA connections. The unit is actually made by CFI in Tiawan and can also be found under different names like Rosewill, CFI and there is a new one under the name Cavalry. These enclosure come in 4, 5 and 8 Bay configurations. If your looking at the 8 bay enclosures then you need to keep one thing in mind and that is for eSATA you need 2 eSATA connections to access all 8 bays but with USB you can access all 8 bays with only one connection. eSata connectins are faster and even if the newer enclosure is USB3 it will only run at USB2 speeds on your server. Whats interesting is that these units are sold with or without the RAID card so look for the models which do not come with the RAID card as most people never use this card and there is a substantial reduction in price. If your server has no eSATA connetion then you will need a RAID Card which supports JBOD for use in WHS and so you will have to determine if the RAID card supplied with some of the units is right for you or not.
If you run down the listing in the following link you will see other enclosures which are available to you. http://www.newegg.com/Product/ProductLi ... gesize=100
This will get you started so that you can expand your search to find the unit which best fits your budget and needs. Since your now in an expansion mode you may also want to take the time to review your growth and if you are happy with the current performance of your server. I mention this because far too often people end up with many external enclosures and drives then they look towards building a large enclosure server so they can put everything under the hood of one unit and at the same time boost their server perfomance. Sometimes you will find the total cost of expanding outside the box will often make for a very nice down payment towards a larger system so its worth thinking about. On the other hand if your growth needs are limited then just adding another 5 bays may be whats best for you.
I wish you luck in determining which unit is best for you. Please feel free to ask many questions before you buy so that you will have made a well informed purchase and not have buyers remorse later.