Best ship in PG now is Ancient Punisher. Its 1.6 million Cryo. So this is money you must have with you while jumping planets searching this ship and its BPs. About Parsec class, only Constructor is worth double more money than Punisher, because Giza cannot be easily shot without Constructor. It can heal aggro player who gets most damage, and others with repair field.
Other parsec class ships were good some years ago when Draconis system started. You didnt have ship when start to play in Draconis, but who had Parsec class ship, played a lot easier, because they had 20% more armor on top of common Deluvian.
Now, in Sirius many of them are out of use, so if you havent bought one, you better save Cryo for Sirius class. Raider and Punisher are best Sirius ships that exist. Raider have 3 more weapons that are coming from Giza, and 1 that coming from Strong units. (If you have middle weapons with number 3, stronger with 4, and best 5, then it will be 5,5,5,4) Its very strong ship. His armor is same as Parsec defender with 4th armor, that means bigger than Parsec Storm, Terrorizer, Engineer and Sniper. And it cost half.
Dominator can also give you cool play, but it cant do anything for other players, cant heal them, cant cover them. It don't have firepower, and by many players it is known as "P.... Wagon"
The only reason why Parsec class ships are so expensive is that they are available in shop and there is a possibility that when new system comes (Tau Ceti), their armor will be increased, so then they will be stronger in Sirius. But, would they be stronger then Tau Ceti ships I wonder?