Mike,
Your question is a valid one, and from my understanding, the addition of a 35550 in front of your 40250 has only one advantage, but several disadvantages. A surge protector has a joules rating new an that capacity is diminished by every power surge that it absorbs until it no longer offers protection at which point most, but not all units just disconnect the power source. The obvious advantage of having the 35550 in front of your 40250 is that a surge will diminish its capacity instead of diminishing the capacity of your 40250. The down side is that you are duplicating several features that are not necessary, add expense to the installation, and will be a irritant to most people like the delay time on power engagement. My suggestion would be to just look for a surge protector that is only a surge protector with little to no other features. However if the redundancy of features does not irritate you, it will work.
Gerald