The 24 bit PMD671 is a big improvement over the 16 bit PMD670 and PMD660. It's got a much better preamp than either of the 16 bit models.
Online prices for the PMD671 vary from around $850 to $1000. Occasionally you can find a better deal, like this: A company called Martel Electronics is offering to sell the PMD671 for the same price as the PMD670. A week ago they were advertising a $699 price, but today the web page says to call to get the "special price." Martel is not some fly-by-night eBay merchant, they're an established company that sells gear for dictation and court reporting. Here's the link.
http://martelelectronics.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=988If you're considering spending $850 or more on a recorder, then check out the Tascam HD-P2. It's becoming a favorite of professionals who do field work on movie and TV production. The HD-P2 is similar in price and features to the PMD671, but (IMHO) has better-sounding preamps.
This forum includes several people who are very happy with the upgrades Doug Oade performed on their machines. In particular, the Advanced Concert Mod is a great upgrade if you plan to record loud concerts. With a few exceptions, Oade won't work on machines that he didn't sell originally, so you might want to shop at
www.oade.com for your Marantz or Tascam equipment even if it means paying more.
Flintstone