I recently bought a Pro 651 and am very pleased with it so far. After fretting over the Phase I vs Phase II issue, I finally called some one local and was told we would not be going to Phase II, period. With that info in hand, I began researching Phase I scanners. Here's what I found.
Pro 106 was made by Grecom for Radio Shack.
Pro 651 was made by Whistler for Radio Shack, replaces Pro 106.
PSR 500 was made by Grecom for their scanner line.
WS 1040 was made by Whistler for their scanner line, replaces PSR 500.
All these scanners are essentially the same. The 651 may have updated hardware, but not sure.
Marketing wise, PSR 500s are getting rare online, as are 106s. 1040s are a current product and are quite pricey. However, the 651 seems to be under the radar and many new in box examples are available on eBay. I bought one of these, for around $200. It is not a refurb.
What can I say for a review? The scanner is fairly easy to program through the keypad for a basic trunking scanlist. The menu system saves a lot of time when tuning up the details of talk groups and how they are handled. The included antenna is crap, and I am getting better reception using a dual band ham antenna for 2 meter/440. Depending on where in my house I listen, it varies from occasional dropped traffic, to perfect reception. Audio quality is good. It works with all the power accessories I have for my older Shack scanners, including outboard battery pack, 9 volt AC adaptor, 4 AAs, and has the black and yellow battery holders. No cable was included, but Radio Shack has an eBay store with prices about $5 lower than online. Cable is $24 online. Cables from older Shack scanners are not compatible, as these cables use full duplex to the scanner, and allow computer control of the scanner while scanning. Also, Shack sells a 800mhz antenna for scanners, $20 eBay with free ship, that is very well reviewed by Eham members and I have one on order, again $5 less than Shacks website or stores. For AC adaptor, search eBay for Nikon EH52 AC Adapter. These work fine, and can be had 2 each for $10 with free ship.
If this scanner lasts as long as previous Gre/Shack scanners, I'll be well pleased, as my Pro95 is now 20 years old and still going. Based on my brief experience with this unit, I highly recommend it.
Joe