Awaz,
I purchased 2 helmets from Motorcycle Super Store a couple of years ago, after going to a local dealer and determining the correct model and size. What I received from that order was much smaller, and did not fit, even though it was labeled as the same size, same brand, same model. I had to pay to return them, and they would not honor their sale price to replace them with one size larger (the sale had ended).
I was very unhappy with them for not simply exchanging the helmets. After some serious complaining to them about the issue, they had another "sale" a couple days later, putting the helmets back to the price I originally paid. Not sure if they did this just for me, or if they had planned it all along, but I did finally get the replacements at the original purchase price.
I don't know why the size from them was smaller than what I tried on at the local dealer, but I suspect they had models from prior years, possibly old stock from the manufacture they were selling off cheap.
I've used HJC helmets, including modulars (Symax), for years, and although they worked well, they had issues (broken gears in the jaw mechanisms, broken release cables). I could not find all the replacement parts needed to fix them, so I moved on. I actually repaired the broken release cable with dental floss, and it's still working!
I'm now using the Scorpion EXO-900. I'm very happy with it, and will probably buy another to use as my snowmobile helmet. First, I will be buying a Scorpion EXO-100 for the upcoming hot summer rides though.
Even though funds are the primary issue for you, don't ignore your comfort factor. Wearing an uncomfortable helmet, just because it was cheap, will completely ruin a great motorcycle riding experience. If you get one that fits well, but has a couple of 'pressure points', you can always sand down the Styrofoam behind the padding to give a little more clearance. It doesn't take much to make a dramatic difference.
Hope this helps.