Ive found this thread interesting for a few reasons.
I owned a 300rwkw 300zx before my LS1 and for a long time I loved blitzing the 8's where the driver seemed to think because it said "v8" on the badge it meant it would be the fastest thing on earth. I basically needed a sporty family sized car and ive always wanted to own an 8 so here I am.
My brother owned a cast iron VS 5ltr v8 which was extensively worked, it did 160km/h maxed out had everything bar blower or turb done. I likened it to a vx SS 250kw.
I now own a Senator VY and im struggling with the low power but as people have said its relative to what you are used to.
Mods wise from what I have gleaned, the best $$$ vs bang mods are improve intake through OTR or double hole mod or open airbox and pod with a mafless tune. Next is a cam and change the diff ratios to give you the fast feel by the seat of the pants-o-meter.
These are the mods I will be doing to mine funds permitting, and then I will be happy with its power output which should raise to close to the 300rwkw im used to.
I also drew the line with the interior type, I didnt want to get a round interior commy as I felt it would date too quickly I wanted a square interior one as there is only the new VE interior, but if I got a round interior id be 2 generations old already for resaleability.
I dont like the VZ SS look with the bonnet bump lines, but hey this isnt an opinions on my likes dislikes car thread.
I recon the VY SS is a good buy if funds wont permit getting an entry model VE. Even better if you can get the Senator or GTS they are loaded with alot of stuff the SS and even the baseline clubby isnt.
Another option is to look for the late 2004 LS2 VY that would be better than a 5.7 to start with for sure.
My sister has the VE Omega v6 and it is very pokey for a 6. I can only imagine what it would go like with some mods. It feels like a cast iron 5ltr in stock form.
Sounds like you are on the right track.