I agree with the others: if you are interested in using the Zone System, a spotmeter is almost essential.(posted 8332 days ago)Of the Pentax spotmeters, the digital is far more desireable, although, it's more expensive.
The Sekonic meters are very nice too. My one objection to the 508 model is there is no readout in the finder, so you have to take a reading, then look at the display on the side of the meter. This is very inconvenient. The new one--the 608--corrects that deficiency, but it costs $600! The 508's incident feature is occassionally useful, but if you use it, you might easily forget to switch it back, and if you do, it's very easy to make a huge mistake in metering. The only indicator as to which mode you are using is a tiny illustration in the display window, which is very easy to overlook. I don't know if the 608 addresses this problem. Otherwise, these are very nice meters and they are well sealed against dust and moisture.
Another very good alternative is the Minolta Spotmeter. It has a digital display in the finder as well as on the side. It's well made and accurate. You can also find them readily on ebay selling for about $250. A new one at B&H is about $400.