Yeh I kinda get the impression you are similar to me in that you are going to need vibrations that are more rumbly and travel deeper into your clitoral tissue. Everything you say here (The pushing the toy in harder, the wishing for more power etc) Two things:
First of all I would recommend practicing reaching orgasm gently. Whenever you have the time or inclination, try different techniques because it is possible to become accustomed to needing bloody intense vibrators after a while, if you only use powerful toys, you know what I mean?
But in the meantime you want to get yourself a more powerful and potentially less surface level buzzy vibrator. The problem is, these are gunna cost you a little more than the Lustfinger. Here are some recommendations:
Probably the best bullet vibe ever (Although I have not tried this one, I have this on good authority):
http://www.lovehoney.co.uk/product.cfm?p=20778&reviewpage=1#customer_reviews
Apparently it is simply not like any other bullet vibe, my friend is a serious power lover, like me she cannot cum from shallow teasing vibes and I was saying to her "Pfft, its a bullet, it cant be that powerful" then a few other trusted ladies joined the conversation to confirm that yes...yes it really is. (Its on my list now lol)
http://www.lovehoney.co.uk/product.cfm?p=20464
The king of powerful and deep vibrations. It starts off nice and gentle and can be turned up vibrate your socks off. I cannot even have it on its highest setting, it is that strong. )Prob one of the strongest vibes available, unless you count full on sex machines which costs hundreds, thousands)
http://www.lovehoney.co.uk/product.cfm?p=12129
I personally love the Gigi for clitoral stimulation and it has reasonably deep vibrations and hasnt failed me yet.
I do realise they are more pricey but you really do get what you pay for. The motors inside are better made and they produce stronger and deeper vibrations. Also bear in mind that no matter what you buy from Lovehoney, they offer a 365 day return policy and you can return the item for ANY reason (even if its been opened and you just dont like it, or cant get on with it) You can check out info for the return policy here http://www.lovehoney.co.uk/help/returns-policy/ so if you do try something and dont like it, return it, or exchange it no problem.
Basically though, I would advise you to generally avoid bullets and smaller finger vibrators and move up a step to toys with larger, better quality motors. The problem is that big doesnt always mean good. Its hit and miss. The above are my personal recommendations but I am sure the other ladies will have some great ideas too.
Best thing to do as well, is to have a look on the site, choose some toys you like the look of, post us the links and we can let you know which one would maybe be the best, or let you know if they worked for us or not. Im sure bwteen us all we have tried most hehe.