I recently owned a Juki DX5 (when I purchased it, the DX5 was the same price as the F600 - which I was also looking at). I believe the DX5 is slightly upgraded from the F600 (has the hover/pivot feature and you can program in certain things to the foot pedal). I tested this one out locally, and it sewed very well. I will say I really liked the feed on this machine, as well as the 1/4" setting (I don't know if that 1/4" setting is on the F600). Gave me a perfect scan 1/4" seam with my fabric following along the edge of the foot. The F600 gets really good reviews (as does the DX7 - which is the same as the DX5 but with more stitches, more lighting, extension table).
A couple of things I did not like with my DX5 (in case this matters to you). You cannot lower the needle without the presser foot being down. I found this to be an irritation when I wanted to bring up the bobbin thread (and the hand wheel was very tight to turn to do it manually, even though the manual indicated this was one way to bring up your bobbin thread). You don't have to bring up the bobbin thread, but I also found that starting to sew without holding a thread resulted in a little bit of a nest at the beginning of a seam (which I think will happen with most machines).
I had some stitching issues out of the box and a faulty needle up/down button. The dealer replaced the first machine (which had both issues), but the second machine also had stitching issues, which the dealer was able to fix with some adjustments. The only other weirdness was that with the presser foot up, if I needed to pull out additional thread through the needle, the thread did not pull through easily (it felt like I was trying to pull thread through with the foot down, even though it was up). I do not know if this is particular to all Juki machines, or if it is particular to the machine I had (and perhaps another adjustment was needed). I just know that wasn't right.
Lastly, the machine will not remember the last settings you were using when you turn it off. I have another machine that does remember, and being accustomed to that feature, I missed it on the Juki. Had I loved the machine, that would not have been a deal breaker.
The Juki did have a nice stitch (after the dealer adjusted). And once the dealer made adjustments, I found I could FMQ easily on it. The thread cutter in the foot petal was quite nice, you get used to that very easily.
I actually tested out a Janome 6700. Very nice machine. I know this one is above what you are looking for, but I have not sewed on a 6500, and it was 3 years ago that I tried out a 6600. The 6700 had a very nice stitch and features. This particular Janome feels quite different from the Juki. The Janome is very quiet compared to the Juki (which wasn't unbearably loud - but louder than the Janome). I think the feed on the Juki is wonderful, could grab edges of fabric easily without eating the fabric. My test on the Janome was short, so I didn't play around with the accufeed, etc. I did try FMQing, and that was incredibly smooth. Even without have a slider mat. Plus you have the extra harp space, which is invaluable for FMQing. While I felt the Juki FMQed very nicely, it has a smaller harp space which could make quilting something a little larger more challenging in the middle section. I have an Elna 740 (which I believe is sister to the Janome 7700). I know on my Elna, I love the accufeed option for attaching quilt binding. Really makes a difference. I do not love it for trying to piece/sew. I find the foot to be too big, I cannot see what I am doing. And to get a scant ¼” seam, it meant that the right edge of the fabric was not on the feed dog (plus I could not see what I was doing). I believe that the accufeed on my Elna is more like the accufeed on the 6600. The 6700 does it better, from what I understand (I don’t think you are stuck with those big feet, I think I have seen reference to a narrower ¼” to work with the accufeed). Also, the 6700 has a different needle plate and narrow foot that give more flexibility in sewing (I think it is referred to as the HP plate, or professional plate). I was out of time that day, I wish I had gotten to test more things out on the 6700. But I think these additional features found on the 6700 might make it worth looking at this machine. Sometimes it is these smaller features that really add to the pleasure of sewing.
Honestly, I think if you can hold off a little, that might be a good idea. Try out as many other machines as you can locally. Machines in different brands really do have a different feel to them. Also, that gives you more time to really decide what are must haves on a machine. You might decide you want to purchase up a little to allow room to grow into features, or you might decide, as OnebyOne did, that you really don't need some of those extra features (and save some money in the process – more money for fabric!!).
Best of luck in your search, I will be interested to see what you end up with!!