Which to Switch: the Mac or the Act?

We have been very happy with the system for a year with no complaints. But, its been a year without tinkering and we're feeling the "what if" itch that keeps this industry in business. Right now its an all American mix and match potpourrie:

CJ Act 2 Series 2
Pass XVR-1 (external cross-over)
McIntosh MC452

I am considering either: (i) replacing the Act 2.2 with ARC Ref 5 SE; or (ii) replacing the MC452 with Pass X250.5. Can anyone comment on what we might expect by way of change? How the sound might differ, pros/cons, etc? For example, re preamp, will there be audible synergies by mating the CD8 with its ARC brother Ref 5 SE (presumably yes, but enough improvement at the margin)? Or, re the amp, we like the MC452 a lot (and it would go into a second system, not leave the premises), but we have never had Class A in the house(the X250.5 is Class A up to 15 watts), and the folks at Pass were so helpful in guiding me through the XO set up that I'd simply like to give Pass the business (space constraints rule out the X350.5).

We listen mostly to rock, jazz and Broadway at moderate listening levels, but do crank it up on Saturday nights. Prefer slightly warm side of neutral(emphasis on slightly). Speakers are Linn Akurate 212 with JL F112 sub. Any input is appreciated.

Personally I think you are going about this the wrong way, you have good components, but your speakers are lacking.

The concept of a small bookshelf plus s sub woofer does not equal the same performance of a truly dynamic floor standing loudspeaker.

I would look at upgrading to a new pair of loudspeakers.
Sell the MAC buy the Pass.
What do you use the xover for?
Keep the Mc and buy the ARC. Have heard the Ref 3 with the 402. I can only imagine that the Ref5 with a 452 would sound even better still.
Sell the Act 2.2, and buy the AR Ref 5SE. By doing so, you can go balanced from your CD8 to the Ref 5SE and then to the MC452. All 3 of these components work best in the balanced mode. Audio Research components have always worked best balanced. The MC452 plays best balanced and that is the way I'm using my 452.
Zd542: the Pass XVR-1 takes care of two birds with one stone: (1) the Linn Akurate 212 is a monitor, and the XO splits the signal (I have it set at 78 Hz, 18 db slope) to relieve the monitors of bass duty, and the JL F112 handles all the low stuff; and importantly, (2) resolves (completely) an otherwise serious impedance mismatch between the Act2.2 and the MC452. This XO is capable of literally thousands of different cross over configurations, but each micro adjustment requires one to remove the hood and manually switch the jumpers on the circuit board, and it takes a lot of trial and error to find just the right setting to one's liking. It is not for the squeamish. I am squeamish, and Pass was great guiding me through the month-long process (am less squeamish now).

Thanks all for Mc/Act input so far. Would appreciate others' thoughts as well.
The reason I asked about the xover is to find out if its part of the overall sound of your system. It clearly is. I've had Pass gear in the past, but have no experience their active xovers. I have to assume that besides doing its job as a xover, it has to have some effect on the sound of the system. I just don't know what that is. Given that, any input from me would just be a guess. The components we are talking about here are fairly costly. The only thing I can say for sure is that I would take my time and not change anything until I had a chance to demo it in the system first; espically since you are already happy with what you now have.
Save your money. If it were me, I wouldn't do anything. Why tinker with success. You have a very nice system.
I recently purchased AR Ref 5SE for use with my MC452 and am very happy with it. I use bookshelf speaker and sub-woofer combination (Focal Diablo Utopia 3 + JL Audio f113 with Bryston 10-B SUB active xover) but never feel the speakers lacking.
Pass all the way!!