Cheryl:
First, I think you have to find what works for you. Everyone has a different body type and what might work for one of us won't work for another.
BUT since you ASKED....We have a Smith machine/free weight area down in our basement so about 2-3x a month I will work my chest area and back area down there. However, MOST of the time I use the PS series to work chest and back for my "heavy" lifting and then I'll use the CTX series to work chest and back for my "endurance" lifting. I've noticed (for me) that it's given me some bulk (which I tend to need) PLUS the CTX helps with giving me definition (and even some vascularity which I love!)
Here's an example of what I do:
Monday: PS Chest/PS Back/CTX Shoulders (I LOVE CTX Shoulders!)
Tuesday: PS Biceps/CTX Triceps - 30-40 minutes of cardio (whether it be a Cathe tape or whatever)
Wednesday: 60 minutes of intense cardio (sometimes kickboxing, sometimes stepping...depends on the mood)
Thursday: CTX Chest/CTX Back/CTX Shoulders
Friday: CTX Biceps/CTX Triceps - 30-40 minutes of cardio
Saturday: Something like Circuit Max/Body Max/Interval Max/Cardio Kicks (not ALL of them...just one!)
Sunday: Leaner Legs
Now of course that's if I work out 7 full days in a week which NEVER happens! So usually one bodypart or so doesn't get worked twice in a particular week...so I just make sure that bodypart gets worked twice the following week.
Also, you have to keep in mind that I've been doing this for 20 years and started out with a primary interest in bodybuilding back when I was in my 20's (and had much more energy and MUCH less responsibilities in life!).
What I would love to do (and I don't even know if they have anything like this around) is get into a Ms Fitness competition for women who are 40 and over....Not to win or anything, just something to set a personal goal for....Anyone know of anything like that????
Also, you asked when I started to see changes in my body after working bodyparts twice a week....I would say within 3 weeks....
Hope I didn't confuse anybody...and please keep in mind that I'm not an expert on this or anything. I've just been working out for a looooonng time and have gotten to know my body fairly well.
Terri