I'm just wondering if a subwoofer is necessary in a Home Theater system? I am planning to purchase the M60's as fronts and VP150 center but want to know if I should keep my 50W subwoofer connected or simply use the M60's for all bass.

Thanks.

a 50W sub might be rather underpowered considering your M60's and VP150's are quite powerful. A sub will definitely full up the sound in the lower end, especially on explosions, or any music with bass. Remember, a sub isn't just for rap and hip hop so it can thump away and make your house vibrate while you can't hear any midrange or treble. A good sub will really complement your system. I would suggest the EP350 by Axiom, but if you are on a tight budget, the EP175 will definitely suffice.

You said that a sub would help in the lower end, however, both the EP175 and EP350 go only just slightly lower than the M60's. So how much of an improvement would I really notice?
I remember a couple years ago when I had a center, two floor speakers and two surrounds... the floor speakers shook the room on my HT system. Then I changed and replaced the floor standing and surrounds with four bookshelf speakers- and realized quickly that I needed a sub- and it definitely added the kick to the HT, but music with a sub just plain sucks. I would hate to have to go through the trouble of turning the sub on/off each time I switched between music and HT... so I figured the M60's alone would solve my problem..

if you prefer the sound without a sub, then it is not worth buying. Remember, a sub plays only low bass whereas floorstanding speakers play the entire spectrum of sound. you are right when you say that a sub is more necessary with bookshelf speakers. With the M60's, it's more of a complement to the system, but is particularly usefull when watching 5.1 movies where the subwoofer has its own channel, and all sound below a certain point is sent to the sub.

but, it's really up to you if you want it, and if you can spend the money.

Just because a speaker is listed to play down to a certain frequency doesn't mean that it is better. You need to compare how easily it can do it and what SPL it can put out at that frequency. For home theater a sub is almost always a must. It just adds that extra oomph for the explosions and takes some of the strain off the mains that are trying to do everything.