do I really need this bike?

N+1 and all that...

This ticks several boxes on the reasons to add a new bike to the stable.

1. It's a frame in a material you do not already possess.

2. It has higher level components and therefor is an upgrade.

3. You do not have a back up/rain bike already. This is an opportunity for you to fix that. I bet it would fit fenders nicely.

Sounds like a waste to me.

Have you ever been in a situation where you needed a backup bike? where you had to cancel your ride lacking one?

Steel? sounds like last century - so, you wouldn't race it anyway, who cares about aggressive geometry if it's beyond obsolete for racing. Old parts ... hmm. Aluminum aero ... hmm ... 

Yes!  I didn't have tire levers and I woke up to a flat tire and I couldn't get the tire off and time was ticking and I had a long ride and work afterwards so I just grabbed the old bike.

And I just got hit by a car Saturday using the old bike again while the handlebar arrives to repair the newer bike.

It has come in handy!!

yes you can never have to many bikes the more the merry. I am now up to five bikes.

 Two road 

 two tri

 one hybrid.

Some people actually ride bikes just for the pure enjoyment...

Why does he want triathletes specialist opinions then?

OP, if you're in love then there's no turning back. I don't see the need for such a bike, but if you have the money to spend... *shrug*.

When would you ride it?

If it makes sense that you will use it then get it.

If you are like me that has 5 bikes and only use 2 may just take up more space than adds enjoyment to your life.

I've been a "victim" of N+1 most of my adult life, and I think my count is currently at 9.

That said... I really don't think the components are an "upgrade". 12-year-old 105 group will be 8 speed and well-used, most likely. Your 2011 Tiagra will probably out-perform the older 105 in shifting and smoothness. The Specialized Sirrus wasn't really a high-end steel bike -- it was made as an every-man get-out-and-ride kind of bike. I believe it would also be on a 1" threaded steerer with quill stem -- harder to get upgrade components for that configuration.

But the other side of it is that it's not a POS either. It will probably last a good long time, and you can replace and upgrade components as they wear out or break.

I'd go $350, though, tops.

Well, I am all about adding another bike...but THIS bike? eh. Esp. for $450.

You can do better for that price, should you really want to pick up an inexpensive second bike.

If you really love THIS bike, though...I'd offer less than $400.

I bought a brand new 2010 Marin Lombard (cyclo cross) about 9 month ago for $400.

So I think the orice is high for a bike old, but not yet vintage.

The only important question is: Would this bike be number smaller than 's'. As in numbers of bikes to have is s-1, where 's' is the number when your SO leaves you.

My riding buddy has a different philosophy on the N+1 approach.

N -1 (where N is the number of bikes you own the day your significant other has enough and walks out!)

If you are at N-2 or below the answer to "should I buy that bike?" is always yes!

You've been spending too much time in the pool 

The answer is yes, you need it; you always need it.  

Hah. You must not live in Vancouver! We ride our backup bikes from Oct-March.

IMO, a steel bike is way nicer than an aluminum bike.

Walk Away!

It's not a 'classic' it's just old.  IMO-If you want old-school/steel, look for a Euro manufacturer. (Bianchi, Koga-Myata, Raleigh, Gitane etc). 

Those bikes are just....cooool.