With the current nomenclature the old Silvio 1.5 would be an S45, that is 45 degrees measured from horizontal (V20 is 20 degrees from horizontal, S40 is 40 degrees from horizontal, Q45 is adjustable but 45 is within the range and T50 is the most upright and simplest of the lineup. So the S40 is slightly more laid back than what you have. Keep in mind that these opinions are only what I've picked up from reading as I have a QX100 and a conversion kit. Headrest position is usually more neck-rest than headrest. On the newer models general consensus seems to be that slightly larger tires with lower pressure are better than the suspension in the older models for several reasons: lighter, stiffer power transfer, and negligibly different in actual suspension benefit. I'm not entirely sure that a $10,000 custom suspension wouldn't do better but given the pricing it appears as though the larger tire option deals with the bumps comparably if not better. The rear leaf spring in the old Silvios seems to only have the complaint that they wear out and have to be replaced - not hard but must take a spare if doing a long tour. I'm not sure if the major criticisms of the front shock apply more to the Q. It may be that the front shock on the S was fine but the larger tire was comparable in suspension but simpler and cheaper. So in conclusion:
1. seat angle is backrest angle measured from horizontal like in math class
2. headrest = neck rest - Performance adjustable headrest is a major upgrade by all reports I read in that it is very and easily adjustable
3. There is a performance gain from getting rid of suspension - there may be a very minor suspension difference if compared on back to back rides but won't even be noticeable unless riding back to back.
Again this is info I have gleaned. No personal experience with either model...unfortunately.
