Well I have a couple of suggestions;

Are you focusing on your win-rate? Then you want to get as site that has alot of fish in it and longer blind schedules. I think pokerstars has the best schedules for sitngos however, they are not very fishy. I find Cake or Pacific very soft, however it sounds like you have found a good site in PKR.com
This is a fine entertaining result.

If you are focusing on skill development, Pokerstars. Yes the lower levels are fishy, but the competition for the most part is very good.

If your looking at skills development. I strongly suggest Pokerstars. You can do $1 SnG's and learn alot. Yes you will have some tables that will be pushfest donkements but for the most part you will have tougher competition at these levels.

Some hints;

SnG's are very different then cash games. You really need to have some understanding of mid to late game strategy.

Try and study an hour for each hour you play. Look for articles 2+2 has a ton of them, but you kind find alot on Cardplayer, pokerauthority etc. Look for Colin Moshman or Dan Harrington.

Use a program like SitnGo wizard to critique your play. This involves an ICM to find your equity pushes.

Actual Game Play;

1) Levels until the blinds are 5% of avg stacks, play tight. AA-JJ, AK-AQ

2) Blinds are 5-10% of avg stack, start to open much wider from the c/o or button and the SB if everyone folds to you. You want to steal as many blinds as possible. Fold to any aggression unless you have a made hand (But you want to learn where to resteal here hence the study)

3)Blinds are 10%+ of the avg stack, open push ANY two cards in the SB, open push any pair, 2 broadway cards, AK - AT offsuit and A-x suited from the HiJack, Cutoff and Button. From thwe button you can add suited connectors 78+. From earlier postition you can open push with AK-AJ, KQ-KJ, add through to A9 suited, pairs 88+.

4) Keep in mind the stack sizes. You do not want to push weak into a Bigstack in the BB, or a blind who is 2-5x blinds as you will get called in both situations, keep this in mind and you may want to eliminate open push from the sb or suited connectors from the button.

5) Bubble, many times if the stacks are average you can really open up your standards as you can steal ALOT of chips. Fold to agression but I tend to open every pot for 3-5x blinds depending on position and how passive the table is. It is unbelievable how much people tighten as you get to four runners.

6) DO NOT CALL BETS - MAKE BETS; you need a very strong hand to call or a clear reason, ie mining a set, against a NIT that you can float and push off a hand but for the most part you do not want to call unless you have AA-QQ AK-AQ. You chips are too valuable and you will quickly get commited to a hand in the later stages. Ofcourse, if you have a person before you that is opening all the time you can adjust, but a 3bet is much better then a call.

7) Heads up? I have no idea... I am still trying to learn as my H/U game is a huge leak for me. What I have learned so far is that you want to play a control game, like aikido redirecting your opponents energy and really controlling the action. Remember Q5 is the midpoint, try and get as many chips without showdown.

I hope this helps and somemore will add to it, but this is a basic strategy that should help you crush the $1-5 games.