I looked at WoTWiki, and T54E1 seems to have abysmal pen and even worse turret armour than the T69. The hull isn't good either, and apparently it's not as mobile as other mediums? Should I just free exp to T57 Heavy? I don't want to spend 3.6m only to find out that it still can't pen T9/10 flat frontally (or even some sides)