All-grain question

I've been thinking about getting into all-grain brewing. just wondering if you have to boil all 5 gallons after the sparge or just boil like 3 gallons then just top it off to 5 gallons in the fermenter?

Usually, you get 6 gals after mashing and boil it down to 5 gals.

Yep, you are going to have to spring for the big brewpot.

Concentrated all grain boils are doable but they are hard to control and tend to produce more off flavors.  The hop bitterness and aroma are often off kilter and the head forming proteins take a beating.  You should try it and see if the beer is drinkable to you but be prepared to have a different beer than you set out to make.

I say this to all brewers wanting to go all grain.  Don't!  Unless you can control fermentation temperature.  You will be hard pressed to find it better unless you can control the fermentation.  Remember, fermentation makes beer.  Everything else is just wort.  Having the right amount of healthy yeast in a temperature controlled environment is vital to making good beer. 

Yep you are going have to get the big brew pot  I would go with a 10 gallon  having the extra head-space is great  I will be getting another this year and most likely will get a 15 gallon, ball-valve temp false bottom the whole nine yards.  You will find also that you will get a much better hop utilization doing full boils  I started doing full boils with the MR Beer kits and get hooked on the results

I've got a 9 gallon brewpot and I wish it was bigger.

Ive got a 9gal brew pot also, its pretty decent, still able to get7 gal in pot for boil (6 gal batch) but get a 10 it would be nice to have a little more room.