First of all...welcome to thr iRV2 forum! I feel you have found the best RV forum on the web...
You will find some of us here are pretty knowlegable..while others are not!
(You should be able to differentiate the two groups fairly quickly
As far as the rig you asked about...a friend of ours has a 40' Monaco Knight with the 330HP engine and loves it...so the 300HP on the 36'PDQ should be adequate - as long as you aren't pulling a heavy toad or racing up the mountains. You will NOT be the first one to the top and if you are always in hilly terrain...then this may not be suited for you.
The floorplan seems to be one of the more popular out there... or it is for the manufacturer...there are a lot of them out there...so it must be very livable!
Here is a link to that year Neptune
in case you had not found it yet.
I do hope you find the perfect rig for you...and if it is a Monaco product...then you are certainly welsome to join our "Monaco family" here on iRV2!
Good Luck..and I hope this helped some!