[Premium-Rx] Question on RF-590 filters

[W2HX]

Hi friends,

I just acquired an RF-590 (to replace the 590H I am selling on ebay).  One of the reasons I was interested in the 590 was that it has the ability to have more than one filter per mode. The "H" has only one filter per mode. When I plugged in the new 590 and tested it out, here are the filters it has:

AM         6.0, 3.2, 16
SSB         3.2
FM         16
CW         1.0, .3

I was surprised that I had only one bandwidth for sideband. I would have expected some choice here. I then remembered that I had purchased a spare filter board a long time ago. So I dug it out and took a look. This is what I found.  The 590 seems to have mechanical filters, but this spare board I acquired seems to have crystal filters. Here are some pictures:

http://w2hx.com/x/Harris/RF-590/0511162325.jpg
http://w2hx.com/x/Harris/RF-590/0511162325a.jpg

Can anyone tell me a few things?

1.      When/why/how did Harris have different options for filter technology (crystal/mechanical)

2.      I noticed that both boards seem to have a spare "space" for a filter. Can I put a filter into one of these spots?

3.      If I were to add a filter, how would I know which mode would "see" that filter as available?

Does anyone have a 590 with more than one BW for ssb? I would love to try to use one of the 2.7k filters from the crystal filter board pictured above. But I wonder if I would need two filter slots not just one to handle USB and LSB?
Maybe I would have to replace both 3.2K filters with the two 2.7k filters? If I did that, would the display show the right bandwidth automatically or is there something I would need to do?

I know mechanical filters have very steep skirts. But for general purposes hamming, might the crystals sound better than the mechanicals? Anyone ever play with these two types of filters in a 590?

What can you guys tell me about filters, filter boards, the 590 and all of that?
Thanks in advance!!
Eugene W2HX