Shoot; if you already have a SINAR, it is a no brainer. Wish you would have asked before I sold my whole DB system a few months ago. Some rich 19 year old art student with zero personality ended up getting it for asking price because his teacher told him so! He had a brand new $8,000 Canon + thousands of dollars in lenses, not to mention the Mac, and was pissed that he was being forced to buy a 4x5 by the school. I am sure it will sit forever once he is done with the few classes he needs it for. Really ticked me off, but not enough to say no to the money.
Be aware that the mechanical versions of the shutter max out at '60. You need one of the electronic ones for the faster speeds, and they are more expensive.
I've used packards for years, and like them. I change film speeds to avoid the speed limitations. But I usually shoot asa 25, so th instantanious speed works for me.